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PubMed1996

Isolation of the promoter for Type I hexokinase from rat.

A genomic clone containing sequence identical to the 5' region of the cDNA for rat Type I hexokinase was isolated from a lambda Charon 4A library. A 5.4-kb EcoRI fragment from this clone, containing the matching sequence, was sequenced in its entirety. Rapid amplification of 5' cDNA ends (5' RACE), reverse transcription polymerase chain reaction, and ribonuclease protection experiments were consistent with the existence of multiple transcriptional start sites clustered in three regions approximately 460, 300, and 100 nucleotides upstream from the translational start codon. Together with results of previous work, the 5' untranslated sequence defined in the present study accounts for the 4.3-kb mRNA for Type I hexokinase seen on Northern blots. Fragments from the 5' flanking region were cloned into a reporter vector containing the luciferase coding region. Based on transfection experiments with both PC12 and H9c2 cells, promoter activity was associated with a region lying between nucleotide positions -742 and -516 (with A of the ATG codon at the translational start site defined as +1). The promoter region lacks a TATA sequence and, together with the transcriptional start sites, is located within a GC rich segment (a "CpG island") approximately 1 kb in length. These characteristics have previously been associated with the promoter and transcriptional start sites of genes for "housekeeping enzymes."

Animals↗

PubMed2004

Identification of the promoter region of the human betaIGH3 gene.

PURPOSE: To isolate and characterize the promoter of the human betaIGH3 gene. METHODS: Primer extension and CapSite Hunting methods were used to determine the transcription start sites (TSS) of the human betaIGH3 gene. Putative transcription factor-binding sites and potential promoter regions were identified by online tools. Two clones containing 3 Kb and 1 Kb of the 5'-flanking region of the betaIGH3 gene were isolated and their respective promoter activities were characterized. Various fusion constructs of betaIGH3 promoter-luciferase reporter were made to transfect A549 cells. The responses of these fragments to TGF-beta1 were also measured after being treated with TGF-beta1 at different concentrations. Several human and nonhuman cell lines were also transfected with the 1 Kb betaIGH3 promoter-reporter construct to compare the activity of the betaIGH3 promoter in these cells. RESULTS: The transcription start site of human betaIGH3 mRNA was determined to be 65 bp upstream of the ATG start codon. Both the 3 Kb (-3011 to -1) and 1 Kb (-1000 to -1) fragments displayed strong and comparable promoter activity in transfected cells. Truncation analyses in A549 cells identified the nucleotide region from -336 to -1 as having high promoter activity (minimal promoter). The results also indicated that the nucleotide fragment from -1000 to -646 contained negative regulatory elements. Twenty ng/ml TGF-beta1 upregulated the activity of the 1 Kb construct, but did not upregulate the activity of the -336 to -1 construct, suggesting that TGF-beta1 responsive elements existed in the region from -1000 to -336. The 1 Kb construct universally demonstrated promoter activity in all cell lines tested. CONCLUSIONS: We identified the betaIGH3 gene promoter with a distinct regulatory pattern in the 1 Kb region upstream of the ATG start codon. Further elucidation of the functions of this promoter region may facilitate understanding of betaIGH3 and its related corneal dystrophies.

Animals↗

PubMed1997

Characterization of the promoter of human adipocyte hormone-sensitive lipase.

Hormone-sensitive lipase (HSL) catalyses the rate-limiting step of adipose tissue lipolysis. The human HSL gene is composed of nine exons encoding the adipocyte form and a testis-specific coding exon. Northern blot analyses showed that human adipocytes express a 2.8 kb HSL mRNA, suggesting the presence of a short (20-150 bp) 5' untranslated region (5'-UTR). A single 5'-UTR of approx. 70 nt was detected in RNase H mapping experiments. Two 5'-UTRs of 70 and 170 nt respectively were obtained by rapid amplification of cDNA ends and cDNA library screenings. RNase protection experiments, with probes derived from the two products, showed that human adipocyte HSL mRNA contains only the 70 nt product. Primer extension analysis mapped the transcriptional start site 74 nt upstream of the start codon. In HT29, a human cell line expressing HSL, the presence of the short or the long 5'-UTR is mutually exclusive. The short and long 5'-UTR exons were located 1.5 and approx. 13 kb respectively upstream of the first coding exon. Various portions of the 5'-flanking region upstream of the short product exon were linked to the luciferase gene and transfected into cells that express HSL (HT29 cells and rat adipocytes) and do not express HSL (HeLa cells). High luciferase activity was found for constructs containing the sequence between nt -2400 and -86, but not for shorter constructs. An analysis of 14 kb of genomic sequence revealed the presence of five DNase I hypersensitive sites associated with active gene transcription. Three of the sites are located in the vicinity of the transcriptional start site and could be linked to the minimal promoter activity. Two of the sites are located downstream of the exon containing the start codon, suggesting the presence of intronic regulatory elements.

Adipocytes↗

PubMed2005

Divergent transcriptional and translational signals in Archaea.

Many Archaea, in contrast to bacteria, produce a high proportion of leaderless transcripts, show a wide variation in their consensus Shine-Dalgarno (S-D) sequences and frequently use GUG and UUG start codons. In order to understand the basis for these differences, 18 complete archaeal genomes were examined for sequence signals that are positionally conserved upstream from genes. These functional motifs include box A promoter sequences for leaderless transcripts and S-D sequences for transcripts with leaders. Most of the box A sequences were preceded by a BRE-like motif and followed by a previously undetected A/T peak centred on position -10. Moreover, the sequence of the predominant S-D motifs in an archaeon is shown to depend on the precise number of nucleotides between the conserved anti-S-D CCUCC sequence and the 3'-terminal nucleotide of 16S RNA. Correlations with phylogenetic trees, constructed for the 18 Archaea, reveal that usage of high levels of both S-D motifs, and GUG and UUG start codons occurs exclusively in the shorter branched Archaea. High levels of leaderless transcripts are found in the longer branched Archaea.

Archaea↗

PubMed1998

Characterization of the 5'-flanking promoter region of the rat somatostatin receptor subtype 3 gene.

We investigated the 5'-flanking promoter region of the rat somatostatin receptor subtype 3 (rSSTR3). Using a cDNA probe, genomic clones containing the 5'-flanking promoter region of the rSSTR3 gene were isolated. A sequence of 5.4 kb directly upstream from the start codon was analyzed and two introns were found in the 5' untranslated region (UTR) of the cDNA sequence. The transcriptional initiation site was determined by 5' rapid amplification of cDNA ends (RACE), primer extension and RNase protection analysis with cerebellar RNA. Two major transcriptional initiation sites were found at position 1040 (tsp1) and -856 (tsp2) relative to the translational initiation site. Like a number of other promoters of G-protein-coupled receptors, the rSSTR3 gene lacks TATA and CAAT motifs and includes G+C-rich regions. Functional analysis of the promoter region by transfecting rSSTR3 luciferase-reporter gene constructs into rat pituitary GH3 cells and HEK 293 cells indicated that a 107-bp region upstream of tsp2 was sufficient to drive transcription. Furthermore a 562-bp region at position -1304 to -1865 upstream of the ATG start codon exerted a negative regulatory effect on transcriptional activity.

5' Untranslated Regions↗

PubMed1991

Cytomegalovirus assembly protein nested gene family: four 3'-coterminal transcripts encode four in-frame, overlapping proteins.

The genomic region encoding the assembly protein of simian cytomegalovirus (CMV) strain Colburn has been cloned, sequenced, and found to be organized as a nested set of four in-frame, 3'-coterminal genes, each with its own TATA promoter element and translational start codon, and all using a single 3' polyadenylation signal. The 3' end of the longest open reading frame (1.770 bp) was identical to the 930-bp sequence coding for the assembly protein precursor, as determined from a cDNA clone. The assembly protein coding region of human CMV strain AD169 was similarly organized, suggesting that both viral genomes could give rise to four independently transcribed 3'-coterminal RNAs coding for four overlapping, in-frame, carboxy-coterminal proteins. These predictions were tested and confirmed. Four mRNAs corresponding in size and sequence to those predicted were identified in both human and simian CMV-infected cells by using transcript-specific antisense oligonucleotide probes in Northern (RNA blot) assays. The 5' ends of the three largest of these Colburn transcripts were determined by S1 nuclease protection assays and found to map between the anticipated TATA sequences and corresponding translational start codons. The four predicted overlapping proteins were identified by immunoassays in lysates of simian and human CMV-infected cells by using an antiserum specific for the carboxyl end of the assembly protein precursor. The structural relationship of both sets of proteins was verified by comparing their peptide patterns following protein cleavage at tryptophan residues by N-chlorosuccinimide. The similar organization of the homologous coding regions in other herpesviruses into at least two nested, in-frame, 3'-coterminal genes is discussed.

Amino Acid Sequence↗

PubMed2004

Cloning, characterisation and identification of several polymorphisms in the promoter region of the human alpha2B-adrenergic receptor gene.

Screening of a foetal brain genomic DNA library allowed to isolate a 10-kb fragment of the gene encoding the human alpha2B-adrenergic receptor, that contained 5.5 kb of the 5'-flanking region, the open reading frame and 2.9 kb of the 3'-flanking region. The 1-kb fragment upstream from the start codon was rich in GC, lacked consensus TATA or CAAT box, but contained several Sp1-binding sites. Other potential cis-regulatory elements found in the 5'-flanking region included AP2, USF, Stat-6, NFkappaB and Olf-1. A single canonical polyadenylation signal (AATAAA) was found at position +3252/+3257 and the polyadenylation site was 3274 nucleotides downstream from ATG. Transfection experiments with chimeric luciferase constructs containing various truncated fragments of the 5'-region showed that the fragment -3160/+3 exhibited promoter activity in all tested cell lines and permitted the definition of a minimal 200-bp promoter (-603/-411) containing three putative Sp1-binding sites and two initiator elements. Transcriptional activity of this region was inhibited by the addition of mithramycin, a specific inhibitor of Sp1 binding to GC-rich sequences. The search for sequence variants within a fragment covering 1.7 kb of 5'-flanking region and the coding region allowed us to identify five novel single nucleotide polymorphisms. Interestingly, the G/C substitution at position -98 relative to the start codon was common and in complete linkage with a previously identified insertion/deletion polymorphism in the coding region which was showed to affect alpha2B-adrenergic receptor function. Based on transfection data and computer-assisted sequence analysis, the -98 G/C single nucleotide polymorphism was located within a portion of the 5'-UTR (-127/+3) affecting luciferase activity and it created additional putative binding site for Sp1. However, G/C substitution had no significant incidence on promoter activity in BHK-21 or HeLa cells.

Base Sequence↗

PubMed2003

[Inhibition of invasiveness of human mammary carcinoma cell line MDA435 by heparanase antisense oligodeoxynucleotide].

OBJECTIVE: To evaluate the inhibitory effect of heparanase antisense oligodeoxynucleotide (AS-ODN) on the invasiveness of human mammary carcinoma cell line MDA435. METHODS: The AS-ODN complementary to the start codon region of heparanase mRNA and its control, scrambled nonsense oligodeoxynucleotide (NS-ODN) were designed and synthesized and phosphorothioated. The ODNs were embedded in cationic liposome Lipofectin and transfected into MDA435 cells. The total RNAs and proteins were extracted from the cells 48 hours after transfection and then semi-quantitative RT-PCR and Western blotting were performed to evaluate the heparanase gene and protein expression levels respectively. The invasiveness of transfected MDA435 cells were measured quantitatively by Matrigel invasion assays. RESULTS: The heparanase gene and protein expression and invasiveness of MDA435 cells treated with AS-ODN of different final concentrations were significantly decreased compared with that of the controls (P < 0.01). Besides, the inhibitory effects were significantly different between the cells treated with AS-ODN of different concentrations (P < 0.01). The invasiveness inhibition rates were 34.0%, 57.8% and 79.7% at the cells treated with AS-DON of the final concentrations of 0.1 micro mol/L, 0.2 micro mol/L, and 0.4 micro mol/L, respectively. CONCLUSION: Heparanase AS-DON complementary to the start codon region of heparanase mRNA has a significant inhibitory effect on the invasiveness of human mammary carcinoma cell line in a dose-dependent manner.

Antineoplastic Agents↗

PubMed1984

SV40 deletion mutant (d1861) with agnoprotein shortened by four amino acids.

d1861 is an SV40 deletion mutant which was thought to lack the agnoprotein coding region and was used to verify the role of agnoprotein in the life cycle of SV40. In the present study the region flanking the deletion was sequenced and, in contrast to the available information, it was found that d1861 lacks 12 nt in phase, downstream from the AUG start codon of agnoprotein (residues 347-358). Using the runoff protocol with viral transcriptional complexes (VTC), that in vitro elongate the in vivo preinitiated nascent RNA, it was found that in vivo the major initiation site for late transcription is at residue 325, the same as in wild type (WT). In comparison with WT, d1861 encodes information for agnoprotein shortened by four amino acids and it has been identified in d1861 infected cells. However, pulse-chase experiments indicated that the rate of synthesis of d1861 agnoprotein is slower than that of WT agnoprotein and that it has a turnover rate of 1 hr as compared to 3 hr of WT agnoprotein. The reduced rate of synthesis of d1861 agnoprotein can be explained by nuclease S1 analyses in which the major leader of d1861 16 S RNA, that encodes the agnoprotein, appeared in significantly lower amounts as compared to the major leader of WT 16 S RNA. Furthermore, analysis of the potential secondary structures at the 5' end of the leader of d1861 16 S RNA has revealed stable structures in which the start codon of agnoprotein is sequestered in a stem. The involvement of RNA secondary structures in regulating the synthesis of agnoprotein is discussed.

Amino Acid Sequence↗

PubMed2001

Identification of a neurorestrictive suppressor element (NRSE) in the human mu-opioid receptor gene.

Analysis of the DNA sequence of the human mu-opioid receptor gene (MOR) revealed that a region overlapping the start codon was substantially homologous to a DNA element named the neurorestrictive suppressor element (NRSE) or restrictive element 1 (RE-1). Transient transfection experiments in the L929 and HEK non-neural cell lines showed that expression of a MOR promoter/reporter gene construct was suppressed in non-neural cell lines by inclusion of this MOR NRSE. Expression from a thymidine kinase promoter was also suppressed when the MOR NRSE was inserted upstream or downstream of the reporter gene. The MOR NRSE did not suppress expression of the reporter gene in neural derived cell lines, IMR-32 and Neuro 2a. The transcription factor REST which binds NRSE thereby enacting the suppression of transcription, was encoded in a plasmid and co-transfected into the IMR-32 cells. The REST co-transfected neuronal derived (IMR-32) cells became sensitive to the MOR NRSE mediated suppression of reporter gene expression. Electrophoretic mobility shift experiments revealed that oligonucleotides containing the MOR NRSE were bound by a factor from nuclear extracts of non-neural cell lines, HeLa and Jurkat. This binding was specifically competed by oligonucleotides containing NRSE sequences previously shown to suppress transcription through REST. Thus an NRSE element overlapping the human MOR start codon suppresses gene expression in non-neural cell lines and may help direct neural tissue specific expression of MOR.

3' Untranslated Regions↗

PubMed1991

Sequence and linkage analysis of the Coxiella burnetii citrate synthase-encoding gene.

The nucleotide (nt) sequence of the Coxiella burnetii citrate synthase-encoding gene (gltA), previously cloned in Escherichia coli, was determined. The nt sequence analysis revealed an open reading frame (ORF) of 1290 bp capable of coding for a protein of 430 amino acids (aa) with a deduced Mr of 48,633. Preceding an ATG start codon, a possible transcription start point (tsp) with homology to the E. coli promoter consensus was detected. A poly-purine-rich region occurred immediately upstream from the gltA reading frame and potentially serves as a ribosome-binding site. Additionally, a G + C-rich region of dyad symmetry 3' to the translational stop codon was found that could possibly function as a Rho-independent transcriptional termination signal. A large, nearly perfect, inverted repeat was identified upstream from the gltA tsp and was shown by Southern analysis to be present in multiple copies in the C. burnetii genome. The deduced aa sequence of C. burnetii GltA was optimally aligned with enzymes from various prokaryotic sources and one eukaryotic source (pig heart). Using perfect aa identity, the C. burnetii enzyme demonstrated the greatest homology with GltA from Acinetobacter anitratum (65%). Although only 26% aa identity was seen with the pig heart enzyme, many of the residues identified in ligand binding appear to be conserved. Sequencing studies of a region centered approx. 5.6 kb upstream from gltA revealed an ORF read with opposite polarity that encodes a peptide highly homologous to the C terminus of the flavoprotein subunit of E. coli succinate dehydrogenase. This report represents the first nt sequence analysis of a gene of known function from the obligate intracellular parasite, C. burnetii.

Amino Acid Sequence↗

PubMedDate not supplied

Effect of leader primary structure on the translational efficiency of phosphoglycerate kinase mRNA in yeast.

In order to determine the effect of the nucleotide composition of the 5'-untranslated (leader) region on the translational efficiency of mRNA in yeast, we replaced a large part of the leader region of the phosphoglycerate kinase (PGK) gene by various deoxyoligonucleotides of defined sequence. All mutations left the context of the transcription initiation site and AUG start codon intact. The mutant genes were introduced into yeast cells on a multicopy vector and the ratio of the steady-state levels of PGK mRNA and protein were determined. We found translational efficiency to be unaffected by the presence of either an 18 nucleotides (nt) long polyA or polyC tract or by sequences consisting of mixtures of A and C residues in any proportion. In contrast, a poly U tract, as well as mixtures of U and C residues, reduced translational efficiency by a factor of two to three, presumably by long-range base-pairing between the leader and sequences elsewhere in the coding or 3'-non-coding regions of the messenger. In agreement with this hypothesis, a five-fold reduction in translational efficiency was found for an mRNA carrying a polyC tract in the leader as well as a polyG tract in the trailer, neither of which had any effect on translational efficiency by itself. Therefore, we conclude that the leader and trailer regions (including the polyA tail) of PGK mRNA are sufficiently close to base-pair when containing complementary sequences. The resulting secondary structure evidently constitutes a barrier for incoming 40S subunits on their way to the AUG start codon. The presence of an 18 nt long polyG tract in the leader completely abolished translation of the PGK mRNA in accordance with earlier observations. However, we found that leaders containing up to 40% G residues interspersed with either A or U, still allow highly efficient translation. This value is about four times as high as the average G content of leader sequences in naturally occurring yeast mRNAs. Finally, neither deletion of about 40% of the trailer sequence of PGK mRNA, nor replacement of this sequence by homopolymer tracts had any effect on translational efficiency.

Amino Acid Sequence↗

PubMed2003

Distinctive properties of the 5'-untranslated region of human hsp70 mRNA.

A relaxed cap-dependence of translation of the mRNA-encoding mammalian heat shock protein Hsp70 may suggest that its 5'-untranslated region (UTR) possesses an internal ribosome entry site (IRES). In this study, this possibility has been tested in transfected cells using plasmids that express dicistronic mRNAs. Using a reporter gene construct, Renilla luciferase/Photinus pyralis luciferase, we show that the 216-nt long 5'-UTR of Hsp70 mRNA acts as an IRES that directs ribosomes to the downstream start codon by a cap-independent mechanism. The relative activity of this IRES (100-fold over the empty vector) is similar to that of the classical picornaviral IRESs. Additional controls indicate that this high expression of the downstream reporter is not due to readthrough from the upstream cistron, nor is it due to translation of cryptic monocistronic transcripts. The effect of small deletions within the 5'-UTR of Hsp70 mRNA on the IRES activity varies in dependence on their position within the 5'-UTR sequence. With the exception of deletion of nt 33-50, it is small for the 5'-terminal half of the 5'-UTR and rather strong for the 3'-terminal section. However, neither of these small deletions abolishes the IRES activity completely. Excision of larger sections (>50 nt) by truncation of the 5'-UTR from the 5'-end or by internal deleting results in a dramatic impairment of the IRES function. Taken together, these data suggest that the IRES activity of the 5'-UTR of Hsp70 mRNA requires integrity of almost the entire sequence of the 5'-UTR. The data are discussed in terms of a model that allows a three-dimensional rather than linear mode of selection of the initiation region surrounding the start codon of Hsp70 mRNA.

5' Untranslated Regions↗

PubMed1995

Human immunodeficiency virus type 1 Nef protein inhibits activation pathways in peripheral blood mononuclear cells and T-cell lines.

Human immunodeficiency virus type 1 (HIV-1) Nef protein causes the loss of cell surface CD4 and interleukin-2 (IL-2) receptor (Tac) from peripheral blood mononuclear cells (PBMC) and CD4+ T-cell lines. As both CD4 and the IL-2 receptor play crucial roles in antigen-driven helper T-cell signalling and T-cell proliferation, respectively, the role of Nef in the viral life cycle may be to perturb signalling pathways emanating from these receptors. However, the intracellular targets for Nef that result in receptor down-regulation are unknown. Using a recombinant glutathione S-transferase-full-length 27 kDa Nef (Nef27) fusion protein, produced in Escherichia coli by translation from the first start codon of HIV-1 nef clone pNL4-3, as an affinity reagent to probe cytoplasmic extracts of MT-2 cells and PBMC, we have shown interaction with at least seven host cell protein species ranging from 24 to 75 kDa. Immunoblotting identified four of these proteins as p56lck, CD4, p53, and p44mapk/erk1, all of which are intimately involved in intracellular signalling. To assess the relevance of these interactions and further define the biochemical activity of Nef in signal transduction pathways, highly purified Nef27 protein was introduced directly into PBMC by electroporation. Nef27-treated PBMC showed reduced proliferative responsiveness to exogenous recombinant IL-2. Normally, stimulation of T-cells by IL-2 or phorbol 12-myristate 13-acetate provokes both augmentation of p56lck activity and corresponding posttranslational modification of p56lck. These changes were also inhibited by treatment of PBMC with Nef, suggesting that Nef interferes with activation of p56lck and as a consequence of signalling via the IL-2 receptor. Further evidence for Nef interfering with cell proliferation was the decreased production of the proto-oncogene c-myb, which is required for cell cycle progression, in Nef-treated MT-2 cells. In contrast to the binding characteristics and biological effects of Nef27, the alternate 25-kDa isoform of Nef (Nef25) produced by translation from the second start codon of HIV nef pNL4-3 (57 nucleotide residues downstream) was shown to interact with only three cellular proteins of approximately 26, 28, and 56 kDa from PBMC and MT-2 cells, one of which was identified as p56lck. Also, proliferation and posttranslational modification of p56lck in response to IL-2 stimulation were not profoundly affected by treatment of PBMC with Nef25 compared with Nef27.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed2005

Characterizing the function and structural organization of the 5' tRNA-like motif within the hepatitis C virus quasispecies.

Hepatitis C virus (HCV) RNA is recognized and cleaved in vitro by RNase P enzyme near the AUG start codon. Because RNase P identifies transfer RNA (tRNA) precursors, it has been proposed that HCV RNA adopts structural similarities to tRNA. Here, we present experimental evidence of RNase P sensitivity conservation in natural RNA variant sequences, including a mutant sequence (A368-G) selected in vitro because it presented changes in the RNA structure of the relevant motif. The variation did not abrogate the original RNase P cleavage, but instead, it allowed a second cleavage at least 10 times more efficient, 4 nt downstream from the original one. The minimal RNA fragment that confers sensitivity to human RNase P enzyme was located between positions 299 and 408 (110 nt). Therefore, most of the tRNA-like domain resides within the viral internal ribosome entry site (IRES) element. In the variant, in which the mutation stabilizes a 4 nt stem-loop, the second cleavage required a shorter (60 nt) substrate, internal to the minimal fragment substrate, conforming a second tRNA-like structure with similarities to a 'Russian-doll' toy. This new structure did not impair IRES activity, albeit slightly reduced the efficiency of translation both in vitro and in transfected cells. Conservation of the original tRNA-like conformation together with preservation of IRES activity points to an essential role for this motif. This conservation is compatible with the presence of RNA structures with different complexity around the AUG start codon within a single viral population (quasispecies).

5' Untranslated Regions↗

PubMedDate not supplied

Antisense ferritin oligonucleotides inhibit growth and induce apoptosis in human breast carcinoma cells.

BACKGROUND: Ferritin is the major iron-storage protein which sequesters and detoxifies excess iron that is taken up by cells but is not utilized in normal metabolic processes. Human ferritin consists of various combinations of heavy (FerH, Mr 21,000) and light (FerL, Mr 19,000) chains and excess iron leads to an increase in the synthesis of both heavy and light chains. MATERIALS AND METHODS: In this study four pairs of antisense oligodeoxynucleotides (ODNs) were synthesized: FerH-A1 and FerL-A1 were complementary to the 24-base pair sequence overlapping the starting codons of the FerH and FerL genes, respectively, but the sequences of FerH-A2 and FerL-A2 only covered the coding sequences of the ferritin genes. The corresponding sense chain sequences (FerH-S1, FerH-S2, FerL-S1 and FerL-S2) were used as controls. RESULTS: Treatment with FerH-S1, FerH-A1, FerH-S2, FerH-A2, FerL-S1, FerL-A1, FerL-S2 and FerL-A2 at 40 microM, 25 microM, 30 microM, 17 microM, 45 microM, 18 microM, 40 microM and 26 microM, respectively, for 72 hours resulted in 50% inhibition of DNA synthesis (IC50) in MCF-7 breast carcinoma cells, as measured by [3H]-thymidine incorporation. FerH chain mRNA, FerL chain mRNA and total ferritin protein levels were significantly decreased by the IC50 concentrations of each of the antisense ODNs but were not inhibited by IC50 concentrations of sense ODNs, as measured by quantitative RT-PCR and microparticle enzyme immunoassay. However, antisense ferritin ODNs had no effect on the total iron concentration in MCF-7 cells. Incubation with IC50 concentrations of antisense ferritin ODNs caused reduction in cell volume, condensation of nuclear structures and lower levels of Bcl-2 mRNA and protein compared to control cells, but Bax mRNA and protein levels remained unchanged. CONCLUSION: This study demonstrates that antisense ODNs to ferritin genes are about two-fold more cytotoxic than sense ODNs, and that antisense ODNs are specific inhibitors of ferritin gene expression at both the transcriptional and the translational levels. Further, the antisense ferritin ODNs promote programmed cell death with low ratios of Bcl-2 to Bax mRNA and protein expression providing evidence that antisense ferritin ODNs specifically inhibit MCF-7 breast carcinoma cell growth through increased apoptosis. Finally, since the IC50 concentrations of FerH-A1 and FerH-A2, and FerL-A1 and FerL-A2 are very similar for inhibition of DNA synthesis and gene expression in human breast carcinoma MCF-7 cells, it does not seem necessary for the antisense ODNs to overlap the starting codons of ferritin gene to maximize inhibition.

Apoptosis↗

PubMed1986

Evolution of biosynthetic pathways: a common ancestor for threonine synthase, threonine dehydratase and D-serine dehydratase.

The Bacillus subtilis genes encoding threonine synthase (thrC) and homoserine kinase (thrB) have been cloned via complementation of Escherichia coli thr mutants. Determination of their nucleotide sequences indicates that the thrC stop codon overlaps the thrB start codon; this genetic organization suggests that the two genes belong to the same operon, as in E. coli. However, the gene order is thrC-thrB in B. subtilis whereas it is thrB-thrC in the thr operon of E. coli. This inversion of the thrC and thrB genes between E. coli and B. subtilis is indicative of a possible independent construction of the thr operon in these two organisms. In other respects, comparison of the predicted amino acid sequences of the B. subtilis and E. coli threonine synthases with that of Saccharomyces cerevisiae threonine dehydratase and that of E. coli D-serine dehydratase revealed extensive homologies between these pyridoxal phosphate-dependent enzymes. This sequence homology, which correlates with similarities in the catalytic mechanisms of these enzymes, indicates that these proteins, catalyzing different reactions in different metabolic pathways, may have evolved from a common ancestor.

Amino Acid Sequence↗

PubMed2004

Molecular characteristics of phosphoenolpyruvate: mannose phosphotransferase system in Streptococcus bovis.

To elucidate the regulatory mechanism of catabolite control in Streptococcus bovis, we investigated the molecular properties and gene expression of the mannose-specific phosphoenolpyruvate (PEP)-dependent sugar: phosphotransferase system (PTS). The mannose PTS gene cluster (man) was found to comprise a gene encoding enzyme (E) II AB (manL) and genes encoding EIIC (manM), EIID (manN), and a putative regulator (manO). The gene cluster (man operon) was transcribed from one transcriptional start site, which was located 40 bp upstream of the manL start codon. However, two transcriptional start sites were found between manN and manO in primer extension analysis, and the manO may be transcribed independently from the man operon. The man operon and manO were constitutively transcribed without being affected by culture conditions, such as the sugar supplied (glucose, galactose, fructose, maltose, lactose, sucrose, or mannose), growth rate, or pH.

Mannose↗