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PubMed1987

Expression of three genes for elongation factor 1 alpha during morphogenesis of Mucor racemosus.

Three genes, TEF-1, -2, and -3, encode elongation factor 1 alpha in Mucor racemosus. Neutral and alkaline S1 nuclease analyses revealed that the genetic organization is unique for each of the genes. The number and size of the intervening sequences vary in these closely related genes, which suggests that complex genetic rearrangements gave rise to the elongation factor 1 alpha gene family. Nucleotide sequence data from restriction fragments isolated from the 5' and 3' ends of TEF-2 and -3 confirmed the presence of a second intervening sequence in these genes. These data along with S1 nuclease mapping revealed a region at the 3' end of the three genes which was predicted to be transcribed but untranslated. Unique oligonucleotides containing 19 bases were synthesized to hybridize to this unique trailer region in the elongation factor 1 alpha transcripts. These oligonucleotides were used as probes in standard Northern analysis of RNA purified from M. racemosus cells of several morphological types. It was determined that all three genes were expressed in the cell morphological types studied. However, the accumulated level of transcript derived from each gene varied considerably, with TEF-1 mRNA present in approximately twofold greater quantity than the TEF-3 transcript and up to sixfold greater quantity than TEF-2. The level of TEF-1 and -2 mRNA varied little among the cell morphological types studied, whereas TEF-3 mRNA was present in twofold greater quantity in sporangiospores than in either germlings or yeast cells which had been induced to undergo morphogenesis to hyphae. These data suggest that there is differential expression of the genes encoding elongation factor 1 alpha in M. racemosus. At least one gene, TEF-3, shows a morphology-specific pattern of transcript accumulation.

DNA, Fungal↗

PubMed2006

The genomic termini of wild-type and vaccine strains of measles virus.

The genomic termini from 18 strains of measles virus (MV) including wild-type MVs from the pre-vaccine period, recent wild-type isolates and various vaccine strains were sequenced. The first 25 nucleotides of the 3' terminus and last 52 nucleotides of the 5' terminus were conserved in all of the viruses examined. Nucleotides 26 and 42 of the 3' leader were A and G, respectively, in all genotype A viruses except Edmonston wild-type (Ed-WT). All non-genotype A viruses and Ed-WT had U in both positions. No consistent substitution pattern was found in the 5' trailer region of the genome. The nucleotide substitutions at positions 26 and 42 in the 3' leader region were introduced into a MV-CAT mini-genome to test for their effect on the production of reporter protein in both a vaccinia T7-driven, plasmid-based replication assay as well as in a helper virus system. Regardless of the source of the polymerase proteins or the natural leader sequence of the helper viruses, the mini-genome 26A42G produced more CAT protein than 26U42U. The nucleotide substitution at 26 had the greatest effect on CAT production. These results indicated that naturally occurring nucleotide variations in the 3' leader region can affect the levels of reporter protein synthesis, and presumably affected the level of replication of the virus.

3' Untranslated Regions↗

PubMed2002

Determination of the complete genomic sequence and analysis of the gene products of the virus of Spring Viremia of Carp, a fish rhabdovirus.

The complete genome of spring viremia of carp virus (SVCV) was cloned and the sequence of 11019 nucleotides was determined. It contains five open reading frames (ORF's) encoding for the nucleoprotein N; phosphoprotein P; matrix protein M; glycoprotein G; and the viral RNA dependent RNA polymerase L. Genes are organised in the order typical for rhabdoviruses: 3'-N-P-M-G-L-5'. The short leader and trailer regions of SVCV exhibit inverse complementarity and are similar to the respective 3' and 5' ends of the genome of vesicular stomatitis virus. To verify the predicted open reading frames proteins were expressed in bacteria and analysed with a polyclonal anti-SVCV serum. Furthermore, monospecific antisera against the distinct viral proteins were generated. Comparison of genome and protein confirm the assignment of SVCV to the genus Vesiculovirus.

3' Untranslated Regions↗

PubMed2026

Hijacking pre-tRNA enables LTR-retrotransposon-initiated constitutive heterochromatin formation.

Pericentric heterochromatin serves as a fundamental component of eukaryotic chromosomes, endowing specialized genomic architecture with broad functional consequences. Although it is universally marked by H3K9me3 modification, the underlying pericentric DNA sequences diverge substantially across species. Here, by leveraging a transposition reporter system combined with a genome-wide RNA interference (RNAi) screen, we identified a specialized mechanism for recruiting SUV39H methyltransferase to initiate pericentric heterochromatin formation. This pathway depends on a highly ordered complex comprising the Puf68, pre-transfer RNAs (tRNAs), and the primer binding site (PBS). Puf68 binds with high affinity to poly-U tracts in pre-tRNA 3' trailer, forming a Puf68/pre-tRNA complex that subsequently base-pairs with the PBS of nascent long terminal repeat (LTR)-retrotransposons. Through direct interaction, Puf68 recruits Su(var)3-9 to these regions, catalyzing H3K9 trimethylation. Notably, Puf68 is sufficient to initiate de novo heterochromatin assembly both at pericentric and ectopically integrated LTR-retrotransposon regions. Our findings not only uncover a previously unrecognized mechanism of heterochromatin initiation but also resolve a long-standing question of how hosts harness nascent LTR-retrotransposon transcripts.

Heterochromatin↗

PubMed1993

The 3' untranslated region of satellite tobacco necrosis virus RNA stimulates translation in vitro.

The RNA of satellite tobacco necrosis virus (STNV) is a monocistronic messenger that lacks both a 5' cap structure and a 3' poly(A) tail. We show that in a cell-free translation system derived from wheat germ, STNV RNA lacking the 600-nucleotide trailer is translated an order of magnitude less efficiently than full-size RNA. Deletion analyses positioned the translational enhancer domain (TED) within a conserved hairpin structure immediately downstream from the coat protein cistron. TED enhances translation when fused to a heterologous mRNA, but the level of enhancement depends on the nature of the 5' untranslated sequence and is maximal in combination with the STNV leader. The STNV leader and TED have two regions of complementarity. One of the complementary regions in TED resembles picornavirus box A, which is involved in cap-independent translation but which is located upstream of the coding region.

Base Sequence↗

PubMed2000

Functional analysis of the genomic and antigenomic promoters of human respiratory syncytial virus.

The promoters involved in transcription and RNA replication by respiratory syncytial virus (RSV) were examined by using a plasmid-based minireplicon system. The 3' ends of the genome and antigenome, which, respectively, contain the 44-nucleotide (nt) leader (Le) and 155-nt trailer-complement (TrC) regions, should each contain a promoter for RNA replication. The 3' genome end also should have the promoter for transcription. Substitution for the Le with various lengths of TrC demonstrated that the 3'-terminal 36 nt of TrC are sufficient for extensive (but not maximal) replication and that when juxtaposed with a transcription gene-start (GS) signal, this sequence was also able to direct transcription. It was also shown that the region of Le immediately preceding the GS signal of the first gene could be deleted with either no effect or with a slight decrease in transcription initiation. Thus, the TrC is competent to direct transcription even though it does not do so in nature, and the partial sequence identity it shares with the 3' end of the genome likely represents the important elements of a conserved promoter active in both replication and transcription. Increasing the length of the introduced TrC sequence incrementally to 147 nt resulted in a fourfold increase in replication and a nearly complete inhibition of transcription. These two effects were unrelated, implying that transcription and replication are not interconvertible processes mediated by a common polymerase, but rather are independent processes. The increase in replication was specific to the TrC sequence, implying the presence of a nonessential, replication-enhancing cis-acting element. In contrast, the inhibitory effect on transcription was due solely to the altered spacing between the 3' end of the genome and GS signal, which implies that the transcriptase recognizes the first GS signal as a promoter element. Neither the enhancement of replication nor the inhibition of transcription was due to increased base-pairing potential between the 3' and 5' ends. The relative strengths of the Le and TrC promoters for directing RNA synthesis were compared and found to be very similar. Thus, these findings highlighted a high degree of functional similarity between the RSV antigenomic and genomic promoters, but provided a further distinction between promoter requirements for transcription and replication.

5' Untranslated Regions↗

PubMedDate not supplied

[Case report of accidental stab wound to the heart].

A 33 year-old Polish field-worker was found by his colleagues kneeling in front of his trailer, with a bloody stab wound in the heart region. In spite of prompt surgical intervention, the man died from his injury a few hours later. Upon examination of the dead man's trailer a blood-smeared vegetable-knife was found in the sink, and on the floor, a pullover with a slit-like cut. On the wall hung a jacket on a hook with a cut in the inner surface of the left breast pocket but not in the outside layer. The examination of the clothes, the autopsy and a reconstruction of the sequence of events led to the following conclusion: The knife had been placed into the breast pocket of the jacket with the tip facing downwards. As the man put down a sack of potatoes, the knife hooked into a pre-existing gap in the sack and was driven into the chest cavity by the pressure weight of the heavy sack.

Accidents, Occupational↗

PubMed1992

Pleiotropic effect of a point mutation in the yeast SUP4-o tRNA gene: in vivo pre-tRNA processing in S. cerevisiae.

The expression of mutant tyrosine-inserting ochre suppressor SUP4-o tRNA genes in vivo in S. cerevisiae was examined as a basis for further studies of tRNA transcription and processing. In vivo yeast precursor tRNAs have been identified by filter hybridization and primer extension analysis. We have previously shown that a mutant SUP4-o tRNA gene with a C52----A52 transversion at positive 52 (C52----A52(+IVS) allele) was transcribed but that the primary transcript was not processed correctly. We show here that 5' and 3' end processing as well as splicing are defective for this mutant but that the 5' end processing is restored when the intron is removed from the gene by oligonucleotide directed mutagenesis (C52----A52(-IVS) allele). Our results imply that the C52----A52 transversion by itself cannot account for the lack of susceptibility to RNase P cleavage but that the overall tertiary structure of the mutant tRNA precursor is destabilized by the intron/anticodon stem. A second consequence of the C52----A52 transversion is to prevent complete maturation of the tRNA precursor at its 3' end since intermediates containing incompletely processed 3' trailers accumulate in the yeast cells transformed with the C52----A52(-IVS) allele. A correct structure of the T stem might therefore define a structural feature required for the recognition of the 3' processing activity.

Base Sequence↗

PubMed1985

Purification and characterization of an endonuclease from Xenopus laevis ovaries which accurately processes the 3' terminus of human pre-tRNA-Met(i) (3' pre-tRNase).

We have previously reported that the primary transcript of the human tRNAMeti gene undergoes accurate processing to a mature 72-nucleotide species by activities present in the high speed supernatant of Xenopus laevis ovarian extracts (Zasloff, M., Santos, T., Romeo, P., and Rosenberg, M. (1982a) J. Biol. Chem. 257, 7857-7863). We now report the purification and characterization of the enzyme which processes the 3' terminus of the human pre-tRNAMeti species. The activity has been purified about 500-fold from a high speed supernatant of X. laevis ovarian extracts by standard methods. It appears to function as a single polypeptide with a molecular weight of about 97,400. The enzyme generates the mature 3' terminus with a single endonucleolytic cut, also yielding the intact 3' trailer. The endonuclease has a striking preference for the 5' processed pre-tRNAMeti, exhibiting little or no activity in vitro on the intact primary transcript. The enzyme acts similarly with the pre-tRNAAla species of Bombyx mori, suggesting that it possesses a broad substrate range. The requirement of the 3' processing endonuclease for a processed 5' terminus suggests that eukaryotic pre-tRNA processing should follow an ordered cutting sequence in vivo with processing of the 5' leader preceding 3' end maturation.

Animals↗

PubMed1993

Inhibition of translational initiation in the yeast Saccharomyces cerevisiae as a function of the stability and position of hairpin structures in the mRNA leader.

A new modular in vivo/in vitro expression system was constructed which facilitates studies of the control and regulation of gene expression in the yeast Saccharomyces cerevisiae. We studied the influence of stem-loop structures inserted into the non-translated leader region upon the steady-state levels and translation of mRNAs bearing the cat gene from the bacterial transposon Tn9. mRNA abundance changed relatively little in response to alterations in the leader sequence and structure, whereas stem-loop structures clearly inhibited translation to a degree that was dependent upon the predicted stability as well as the position of the inserted secondary structure. A stem-loop structure with a predicted stability greater than -28 kcal mol-1 and with a stem comprising at least 15 (mainly G/C) base pairs inhibited translation in vivo by at least 98%. A stem-loop structure with a predicted stability of approximately -14 kcal mol-1, whose stem comprised at least six G/C base pairs, inhibited translation in vivo by at least 66%. The hairpins were more inhibitory when placed close to the start codon than when positioned near the 5' end of the leader. An mRNA showing extensive complementarity between the leader and trailer regions was not only poorly translated but also had a steady-state level at least three times higher than the average for all the cat constructs examined. Translation of the various mRNAs in a yeast cell-free system followed qualitatively the same pattern as the results obtained in vivo. The stem-loop structures were far less inhibitory in a reticulocyte lysate system. Overall, the data are likely to reflect the full spectrum of translational activities of yeast mRNAs in vivo determined by secondary structure and emphasize the importance of translation as a control step in gene expression.

Animals↗

PubMed2002

Sendai virus trailer RNA binds TIAR, a cellular protein involved in virus-induced apoptosis.

Sendai virus (SeV) leader (le) and trailer (tr) RNAs are short transcripts generated during abortive antigenome and genome synthesis, respectively. Recom binant SeV (rSeV) that express tr-like RNAs from the leader region are non-cytopathic and, moreover, prevent wild-type SeV from inducing apoptosis in mixed infections. These rSeV thus appear to have gained a function. Here we report that tr RNA binds to a cellular protein with many links to apoptosis (TIAR) via the AU-rich sequence 5' UUUUAAAUUUU. Duplication of this AU-rich sequence alone within the le RNA confers TIAR binding on this le* RNA and a non-cytopathic phenotype to these rSeV in cell culture. Transgenic overexpression of TIAR during SeV infection promotes apoptosis and reverses the anti-apoptotic effects of le* RNA expression. More over, TIAR overexpression and SeV infection act synergistically to induce apoptosis. These short viral RNAs may act by sequestering TIAR, a multivalent RNA recognition motif (RRM) family RNA-binding protein involved in SeV-induced apoptosis. In this view, tr RNA is not simply a by-product of abortive genome synthesis, but is also an antigenome transcript that modulates the cellular antiviral response.

Apoptosis↗

PubMed1991

A 60-kDa protein from rabbit reticulocytes specifically recognizes the capped 5' end of beta-globin mRNA.

The binding of proteins from rabbit reticulocyte lysate to in-vitro-generated beta-globin mRNA and its defined segments was investigated using ultraviolet-cross-linking experiments as well as gel-retardation assays. Under stringent conditions, only three proteins (72, 60 and 50 kDa) were found associated with full-length beta-globin mRNA at different positions. The 72-kDa protein is most likely the poly(A)-binding protein and binds, as expected, to the poly(A) tail, whereas the 50-kDa protein exhibits affinity for the trailer region of beta-globin mRNA. The binding region of the 60-kDa protein is located at the 5' end of beta-globin mRNA. The interaction of this protein is dependent on the presence of the 5' cap structure, as indicated by competition experiments using an uncapped beta-globin-mRNA leader segment. Further competition experiments with beta-globin mRNA, deleted in part in the leader region, suggest that, besides the cap structure, certain sequence elements are necessary for the interaction of the 60-kDa protein and the beta-globin mRNA leader.

Animals↗

PubMed2003

The Arabidopsis nuclear DAL gene encodes a chloroplast protein which is required for the maturation of the plastid ribosomal RNAs and is essential for chloroplast differentiation.

Altered pigmentation is an easily scored and sensitive monitor of plastid function. We analyzed in detail a yellow colored transposon-tagged mutant (dal1-2) that is allelic to the dal mutant previously identified (Babiychuk et al., 1997). Mesophyll cells of mutant plants possess abnormal nucleoids and more but smaller plastids than wild type cells. Plastid development in dal1-2 is not altered in the dark but is arrested at the early steps of thylakoid assembly. The amino acid sequence of the protein deduced from our cDNA clone is 21 amino acids longer than the previously published DAL sequence (Babiychuk et al., 1997) and allowed us to show that DAL codes for a chloroplast protein. The dal1-2 mutation has a global negative effect on plastid RNA accumulation and on expression of nuclear encoded photosynthetic genes. We show that the plastid RNA polymerases, the nuclear-encoded NEP and the plastid-encoded PEP, are functional in the mutant. Precursor 16S and 23S rRNA species specifically accumulate at a high level in the mutant but the 5'-end and the long 3'-end trailer are not modified. We suggest that the dal mutation is involved in plastid rRNA processing and consequently in translation and early chloroplast differentiation.

Arabidopsis↗

PubMed2006

Mouse oocytes within germ cell cysts and primordial follicles contain a Balbiani body.

The Balbiani body or mitochondrial cloud is a large distinctive organelle aggregate found in developing oocytes of many species, but its presence in the mouse has been controversial. Using confocal and electron microscopy, we report that a Balbiani body does arise in mouse neonatal germline cysts and oocytes of primordial follicles but disperses as follicles begin to grow. The mouse Balbiani body contains a core of Golgi elements surrounded by mitochondria and associated endoplasmic reticulum. Because of their stage specificity and perinuclear rather than spherical distribution, these clustered Balbiani body mitochondria may have been missed previously. The Balbiani body also contains Trailer hitch, a widely conserved member of a protein complex that associates with endoplasmic reticulum/Golgi-like vesicles and transports specific RNAs during Drosophila oogenesis. Our results provide evidence that mouse oocytes develop using molecular and developmental mechanisms widely conserved throughout the animal kingdom.

Amino Acid Sequence↗

PubMed1996

Cloning of the murine eosinophil peroxidase gene (mEPO): characterization of a conserved subgroup of mammalian hematopoietic peroxidases.

The mouse eosinophil peroxidase (mEPO) gene was cloned by screening a random-primed bone marrow cDNA library at reduced criteria using a hEPO cDNA. An mEPO cDNA was subsequently used to isolate the mEPO gene from a lambda-genomic library. The mEPO gene displays a high degree of conservation with its human homologue: the transcription units are approximately the same size, conserve the relative size and position of the 12 exons associated with each gene, and at a nucleotide level the mouse and human EPO genes are 86% identical in the protein coding regions and 66% identical in the 3'-untranslated trailer regions. This strong conservation extends to the encoded proteins which show approximately 90% amino acid identity. Expression of the mEPO gene is restricted to tissues containing eosinophil progenitor cells (e.g., bone marrow and spleen), a pattern similar to the expression of another murine eosinophil granule protein, major basic protein.

Amino Acid Sequence↗

PubMed2000

The effects of matrices of paired substitutions in mid-acceptor stem on Drosophila tRNA(His) structure and end-processing.

End-maturation reactions, in which the 5' end leader and 3' end trailer of precursor tRNA are removed by RNase P and 3'-tRNase, respectively, are early, essential steps in eukaryotic precursor tRNA processing. End-processing enzymes may be expected to contact the acceptor stem of tRNA due to its proximity to both cleavage sites. We constructed matrices of pair-wise substitutions in mid-acceptor stem at nt 3/70 and 4/69 of Drosophila tRNA(His) and analyzed their ability to be processed by Drosophila RNase P and 3'-tRNase. In accord with our earlier study of D/T loop processing matrices, we find that tRNA end processing enzymes respond to sequence changes differently. More processing defects were observed with 3'-tRNase than with RNase P, and substitutions at 4/69 reduced processing more than those at 3/70. We evaluated tRNA folding using structure probing nucleases and investigated the contribution of K(M) and V(Max) to the processing efficiency of selected variants. In one substitution (C3A), mis-folding correlates with processing defects. In another (C69A), a disruption of structure appears to be transmitted laterally to both ends of the acceptor stem. Poor processing of C69A by RNase P is due entirely to a reduction in V(Max), but for 3'-tRNase, it is due to an increase in K(M).

Animals↗

PubMed2001

In vitro 3'-end endonucleolytic processing defect in a human mitochondrial tRNA(Ser(UCN)) precursor with the U7445C substitution, which causes non-syndromic deafness.

Eukaryotic tRNAs are transcribed as precursors. A 5'-end leader and 3'-end trailer are endonucleolytically removed by RNase P and 3'-tRNase before 3'-end CCA addition, aminoacylation, nuclear export and translation. 3'-End -CC can be a 3'-tRNase anti-determinant with the ability to prevent mature tRNA from recycling through 3'-tRNase. Twenty-two tRNAs punctuate the two rRNAs and 13 mRNAs in long, bidirectional mitochondrial transcripts. Accurate mitochondrial gene expression thus depends on endonucleolytic excision of tRNAs. Various mitochondrial diseases and syndromes could arise from defective tRNA end processing. The U7445C substitution in the human mitochondrial L-strand transcript (U74C directly following the discriminator base of tRNA(Ser(UCN))) causes non-syndromic deafness. The sequence of the precursor (G/UCU) becomes G/CCU, resembling a 3'-tRNase anti-determinant. We demonstrate that a tRNA(Ser(UCN)) precursor with the U7445C substitution cannot be processed in vitro by 3'-tRNase from human mitochondria. A 3'-end processing defect in this tRNA precursor could thus be responsible for mitochondrial disease.

Base Sequence↗

PubMed1989

Non-enzymatic excision of pre-tRNA introns?

We used human tRNA(Tyr) precursor as a substrate to study self-excision of a pre-tRNA intron. This RNA was synthesized in vitro in a HeLa cell extract. It contains a 5' leader, an intron of 20 nucleotides and a 3' trailer. Self-cleavage of pre-tRNA(Tyr) occurs in 100 mM NH4OAc at a pH ranging from 6 to 8.5 in the presence of spermine, MgCl2 and Triton X-100 under conditions very similar to enzymatic intron excision. The reaction is temperature-dependent, relatively fast as compared to the enzyme-catalysed reaction and leads to fragments which resist further degradation. The detailed structure of all major and minor cleavage products was established by fingerprint analyses. Non-enzymatic cleavage occurs predominantly at the 3' splice site and to a minor extent at the 5' splice site. Other minor cleavage sites are located within the intron and in the 3' trailer. Putative 5' and 3' tRNA halves resulting from pre-tRNA(Tyr) self-cleavage are substrates for wheat germ RNA ligase, suggesting that the cleavage reaction yields 2',3'-cyclic phosphate and 5'-hydroxyl termini. Pre-tRNA splicing endonuclease is believed to cleave both the 5' and the 3' splice site. However, on the basis of our results we propose that this enzyme may support the formation of a pre-tRNA tertiary structure favourable for autocatalytic intron excision and impair unspecific self-cleavage.

Base Sequence↗