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Characterization of the complete genomic structure of human thromboxane synthase gene and functional analysis of its promoter.

Thromboxane A2 (TXA) is a potent vasoconstrictor and mediator of platelet aggregation. Thromboxane synthase (TXAS), which catalyzes the biosynthesis of TXA, is a member of the cytochrome P450 superfamily. We report here the complete genomic structure of the human TXAS gene. The gene contains 13 exons and is 193 kb long, the largest P450 gene ever isolated. The physical localization of the TXAS gene on the genetic map of human chromosome 7 was established. A major transcription start site is located at a motif similar to the initiator element where the transcription factor TFII-I binds. We have sequenced up to 1.6 kb of the 5'-flanking region of the TXAS gene and characterized the promoter activity in a human megakaryocyte cell line and endothelial cells. Our results demonstrated that the nucleotides -248/+137 relative to the major transcription start site conferred a full promoter activity of the TXAS gene. This region was regulated negatively by cis-elements located between -1562 and -248. Moreover, the regions outside -1562/+137 might control tissue-specific TXAS expression.

Base Sequence↗

Expression patterns of the human sarcoma-associated genes FUS and EWS and the genomic structure of FUS.

FUS (TLS) was first identified as the 5'-part of a fusion gene with CHOP (GADD153, DDIT3) in myxoid liposarcomas with t(12; 16)(q13; p11). Homologies were found with the EWS oncogene, which is rearranged in Ewing sarcomas and other neoplasias. The genomic structure of FUS shows extensive similarities with that of EWS, but the exon/intron structures differ in the 5' parts, and overall FUS is smaller than EWS. Exon 3 of FUS corresponds to exons 3 and 4 in EWS. FUS exons 4-6 correspond to EWS exons 5-8. Exons 7 to 15 of FUS are very similar to those in EWS, although the EWS exons are larger than the corresponding FUS exons. FUS and EWS were expressed in all tissues investigated. The transcripts were stable within the 160-min half-life experiments. No or little variation in FUS or EWS expression was seen when resting lymphocytes were activated. These observations indicate that FUS and EWS belong to the housekeeping type of genes. This view is supported by the presence of the housekeeping gene type of promoter region in both genes.

Amino Acid Sequence↗

Genomic structures of synaptotagmin II protein: comparison of exon-intron organization of the synaptotagmin gene family.

Synaptotagmin (Syt) I (or II) is thought to be a Ca(2+) sensor for neurotransmitter release in the rostral (or caudal) region of the mammalian brain. In this study, we first report the genomic structures and the transcription initiation site of the mouse syt II gene. Syt II protein coding regions consist of 8 exons with a total size of about 7 kbp. Exon 2 encodes the transmembrane domain, and exons 3-5 and 6-8 encode the C2A and C2B domains, respectively, although the precise intron positions within the two C2 domains are different. The syt II gene structures are quite similar to the mouse syt VIII and human syt IX genes, but not Caenorhabditis elegans syt I, human syt VII, or the mouse syt III genes, indicating that the exon-intron patterns of the functional domain of synaptotagmins (especially the C2A domain) have not been as well conserved during evolution as among isoforms. The only conserved feature among the synaptotagmin gene family seems to have a single exon that encodes the whole transmembrane domain.

Amino Acid Sequence↗

Genomic structure and expression analysis of the gene encoding a silkworm basic Kunitz-type chymotrypsin inhibitor.

Kunitz-type chymotrypsin inhibitor CIb1 of silkworm Bombyx mori is a basic peptide consisting of 62 amino acid residues. To elucidate the mechanisms of transcriptional regulation of CIb1 gene expression, we cloned it for genomic structure analysis. CIb1 cDNA was used as a probe to screen a BAC sub-library. One positive clone containing the upstream sequences was isolated and the sequence result showed that CIb1 gene consists of three exons spaced by two introns. In the 5'-flanking region, consensus TATA and CCAAT boxes were identified. Other binding sites for transcription factors such as NF-kappaB, GATA, C/EBP, COUP-TF/HNF-4, RORalpha1, SRY, and HOXA3 were also detected. Southern blot analysis suggested a single copy of CIb1 gene in the silkworm genome. Northern blot analysis indicated that the expression of CIb1 gene is transcriptionally regulated during development and is apparently tissue-specific. The CIb1 mRNA was detected in fat body, ovary, trachea, and skin. We furthermore investigated the CIb1 expression profiles after LPS and E. coli injection. The fluctuations of CIb1 transcript in challenged larvae confirm our proposal that CIb1 is an immune responsible gene. According to our data, we discussed the transcriptional factors putatively responsible for the physiological role of CIb1 in the silkworm hemolymph.

Animals↗

What we have learned about prokaryotes from structural genomics.

Five years ago systematic determination and theoretical analysis of all protein structures encoded in model prokaryotic organisms was proposed as a powerful way to obtain new insights into protein function and the variety of protein folds. What has been the pay-off from studying structures in genomic context? Have we learned anything new about protein structure? Can we now predict protein function better? In this contribution, I summarize the status of large-scale structure determination projects on prokaryotes and provide an overview of the main results obtained from experimental and theoretical studies in this dynamic research field.

Bacterial Proteins↗

The mouse Fau gene: genomic structure, chromosomal localization, and characterization of two retropseudogenes.

The Fau gene is the cellular homolog of the fox sequence of the Finkel-Biskis-Reilly murine sarcoma virus (FBR-MuSV). FBR-MuSV acquired the Fau gene by transduction in a transcriptional orientation opposite to that of the genomic Fau gene. The genomic structure of the mouse Fau gene (MMFAU) and its upstream elements have been determined and are similar to those of the human FAU gene. The gene consists of five exons and is located on chromosome 19. The first exon is not translated. The promoter region has no well-defined TATA box but contains the polypyrimidine initiator flanked by regions of high GC content (65%) and shows all of the characteristics of a housekeeping gene. The 5' end of the mRNA transcript was determined by 5' RACE analysis and is located, as expected, in the polypyrimidine initiator site. Furthermore, the sequences of two retropseudogenes (Fau-ps1 and Fau-ps2) are reported. Both pseudogenes are approximately 75% identical to the Fau cDNA, but both are shorter due to a deletion at the 5' end and do not encode a functional protein. Fau-prs is interrupted by an AG-rich region of about 350 bp within the S30 region of the Fau cDNA. Fau-ps1 was localized on chromosome 1 and Fau-ps2 on chromosome 7.

Animals↗

Genomic structure and regulation of a novel human gene, Klp1.

Klp1 (K562 cells-derived leucine zipper-like protein 1) is a transcription factor which binds to the coproporphyrinogen oxidase promoter regulatory element (GGACTACAG). In order to clarify the function of Klp1, we determined the complete human Klp1 genomic structure and regulatory element in the promoter region. The gene spans about 2.4 kb and has three exons. Its promoter region has multiple GC boxes, E2F binding site, one cAMP response element (CRE), and no TATA box with multiple transcription initiation sites, which is characteristic of housekeeping and growth regulating genes. Promoter analysis showed that the promoter was more active in K562 cells entered into the cell cycle by serum stimulation than quiescent cells. Further promoter analysis revealed that CRE at -42 is essential for full promoter activity, and c-Jun and activation transcription factor 1/cAMP response element binding protein 1 proteins bind to this element. These structural characteristics and the promoter function suggest that Klp1 may play a role in cell cycle regulation.

Base Sequence↗

Genomic structure and promoter characterization of the human Sprouty4 gene, a novel regulator of lung morphogenesis.

The expression of Sprouty4 (Spry4), an intracellular FGF receptor antagonist, shows a temporally and spatially restricted pattern in embryonic lung and is induced by ERK signaling. To clarify the molecular mechanisms regulating Spry4 transcription, the genomic structure of the human Sprouty4 (hSpry4) gene was first determined by using the GenomeWalker kit. The hSpry4 gene spans > 14 kb and is organized in three exons and two introns. Multiple transcription start sites were subsequently mapped by 5'-rapid amplification of cDNA ends. Analysis of up to 4 kb of sequence in the 5'-flanking region of the gene showed the presence of multiple potential transcription factor binding sites but no TATA or CAAT boxes. Transient transfection using luciferase reporter gene constructs with progressive deletions of the hSpry4 5'-flanking region revealed that the core promoter activity is located within the proximal 0.4-kb region, whereas the minimal ERK-inducible promoter activity is between -69 and -31. Homology analysis further showed that the core promoter region of the hSpry4 gene exhibits significant similarity to the 5'-flanking region of the mouse gene.

Animals↗

The human ROX gene: genomic structure and mutation analysis in human breast tumors.

We have recently isolated a human gene, ROX, encoding a new member of the basic helix-loop-helix leucine zipper protein family. ROX is capable of heterodimerizing with Max and acts as a transcriptional repressor in an E-box-driven reporter gene system, while it was found to activate transcription in HeLa cells. ROX expression levels vary during the cell cycle, being down-regulated in proliferating cells. These biological properties of ROX suggest a possible involvement of this gene in cell proliferation and differentiation. The ROX gene maps to chromosome 17p13.3, a region frequently deleted in human malignancies. Here we report the genomic structure of the human ROX gene, which is composed of six exons and spans a genomic region of less than 40 kb. In an attempt to identify possible inactivating mutations in the ROX gene in human breast cancer, we performed a single-strand conformation polymorphism analysis of its coding region in 16 sporadic breast carcinomas showing loss of heterozygosity in the 17p13.3 region. No mutations were found in this analysis. Five nucleotide polymorphisms were identified in the ROX gene, three of which caused an amino acid substitution. These nucleotide changes were present in the peripheral blood DNAs of both the patients and the control individuals. In vitro translated assays did not show a significant decrease in the ability of the ROX mutant proteins to bind DNA or to repress transcription of a driven reporter gene in HEK293 cells. Despite experimental evidence that ROX might act as a tumor suppressor gene, our data suggest that mutations in the coding region of ROX are uncommon in human breast tumorigenesis.

Basic Helix-Loop-Helix Leucine Zipper Transcriptio↗

[Complete nucleotide sequences and genome structure of two Chinese tobacco mosaic virus isolates deduced from full-length infectious cDNA clones].

The complete nucleotides of two Chinese tobacco mosaic virus (TMV) isolates, TMV-Cv (vulgare strain) and TMV-N14 (an attenuated virus originated from a tomato strain), were determined from their respective full-length infectious cDNA clones and compared with published TMV sequences. The genome structure of TMV-Cv contained 6395 nucleotides, in which four functional open reading frames (ORF), coding for replicase (126 kD/183 kD), movement protein (MP, 30 kD) and coat protein (CP, 17.6 kD) respectively, could be recognized. TMV-N14 contained 6384 nucleotides in its genome. In contrast to TMV-Cv, five functional ORFs encoding the replicase 98.5 kD/126 kD/183 kD, MP(27 kD) and CP(17.6 kD), respectively, were detected in the TMV-N14 genome. TMV-Cv is 99% homologous to a Korean TMV isolate belonging to the vulgare strain at the nucleotide level. TMV-N14 is 99% homologous to a highly virulent Japanese isolate TMV-L (tomato strain) at the nucleotide level. In TMV-N14, one opal nulation (UGA) occurred in the replicase gene and one ochre nutation (UAA) in the MP gene. The former mutation created a potential, additional ORF within the replicase gene, the latter reduced the size of the MP to 27 kD. In addition, there were also 13 amino acid substitutions in the replicase gene of TMV-N14 when compared to that of TMV-L. Collectively, these changes may have significant implications in the attenuation of the virulence of TMV-N14.

Amino Acid Sequence↗

The human RAP250 gene: genomic structure and promoter analysis.

Ligand-induced gene activation by nuclear receptors involves the recruitment of coactivators to hormone bound receptors. Recent results have shown that RAP250, also termed as ASC-2/PRIP/TRBP/NRC/AIB3, plays a critical role as a coactivator of nuclear receptors. In this study, we have determined the genomic organization of the human RAP250 gene in order to identify the promoter region. By searching the GenBank database for EST sequences, we could identify two previously unknown exons in the 5'-end of the gene. Our results show that the RAP250 gene consists of 15 exons spanning 111 kb. All sequences of the splice donor and acceptor sites fit the GT-AG role for splicing. We also show using linkage analysis that the mouse Rap250 gene is located on chromosome 2 close to the agouti gene. The RAP250 promoter is GC-rich and TATA-less, and contains multiple Sp1 binding sites and a MYC binding site. A reporter plasmid containing the 5' flanking region of the RAP250 gene showed significant activity compared to pGL3-basic and minimal thymidine kinase (TK) reporter plasmids in transfection experiments using luciferase reporter genes. Our data show that the RAP250 has a complex genomic structure with a promoter that is regulated by multiple transcription factors for its basal expression.

5' Flanking Region↗

Genomic structure and transcript variants of the human methylenetetrahydrofolate reductase gene.

The human 5,10-methylenetetrahydrofolate reductase (MTHFR) represents a major enzyme in the folate-dependent regulation of methionine and homocysteine concentrations. Different MTHFR mutations lead either to severe homocystinuria as a multisystem disorder or to moderate hyperhomocysteinaemia, which is a common risk factor for disorders ranging from cardiovasculopathy to spina bifida. The N-terminal part of the human MTHFR gene is incompletely characterised. We report the completed genomic structure of this gene including three novel exonic sequences on the basis of a 5'-RACE and a 4.2 kb cloned fragment of human genomic DNA. We demonstrate the existence of four MTHFR transcripts differing in their first exons. The diversity of transcripts is due to alternative transcription initiation and alternative splicing. Three putative polypeptides of 657, 698, and 680 amino acids are encoded. The novel genomic sequence described here includes putative promoter regions as suggested by the presence of regions homologue to binding sites for SP1, AP1, AP2, CAAT or GC boxes. Furthermore, we provide evidence that there are no TATA-box elements to regulate the human MTHFR gene. The results of our study render the full-length characterisation of affected alleles in severe homocystinuria and moderate hyperhomocysteinaemia due to MTHFR deficiency and provide a basis for investigating the regulation of the human MTHFR gene.

Base Sequence↗

Genomic structure of the human BCCIP gene and its expression in cancer.

Human BCCIPalpha (Tok-1alpha) is a BRCA2 and CDKN1A (Cip1, p21) interacting protein. Our previous studies have showed that overexpression of BCCIPalpha inhibits the growth of certain tumor cells [Oncogene 20 (2001) 336]. In this study, we report the genomic structure of the human BCCIP gene, which contains nine exons. Alternative splicing of the 3'-terminal exons produces two isoforms of BCCIP transcripts, BCCIPalpha and BCCIPbeta. The BCCIP gene is flanked by two genes that are transcribed in the opposite orientation of the BCCIP gene. It lies head-to-head and shares a bi-directional promoter with the uroporphyrinogen III synthase (UROS) gene. The last three exons of BCCIP gene overlap the 3'-terminal seven exons of a DEAD/H helicase-like gene (DDX32). Using a matched normal/tumor cDNA array, we identified a reduced expression of BCCIP in kidney tumor, suggesting a role of BCCIP in cancer etiology.

Alternative Splicing↗

Genomic structure and characterization of the promoter region of the human NAK gene.

NAK has been identified as an IkappaB-kinase activating-kinase that plays an important role in NF-kappaB activation in response to several pro-inflammatory cytokines such as TNF-alpha. We describe here the genomic structure of the human NAK gene and analysis of the promoter. The gene spanned 40.5 kb and contained 21 exons with lengths ranging from 39 to 196 bp. Comparison of the phase and position of intron insertions within the human NAK gene with those within IKKalpha, IKKbeta and IKK epsilon indicated that the exon/intron organization of IKK epsilon is more highly conserved than that of IKKalpha or IKKbeta. The transcriptional start site was mapped at a position about 98 bp upstream from the translation start site by means of both an RNase protection assay and a primer extension method. Fluorescence in situ hybridization using full-length human NAK cDNA as a probe showed that the human NAK gene is localized to human chromosome 13q14.2-3, a region in which the loss of heterozygosity is associated with squamous cell carcinoma and leukemia. By using a series of deletion constructs in performing a reporter assay, a minimal 77 bp upstream of the transcriptional initiation site was shown to contribute to the major promoter activity.

5' Flanking Region↗

Genomic structure and alterations of homeobox gene CDX2 in colorectal carcinomas.

Expression of CDX2, a caudal-related homeobox gene, was found to be decreased in colorectal carcinomas. Heterozygous null mutant mice as to Cdx2 develop multiple intestinal adenomatous polyps. To clarify the role of CDX2 in colorectal carcinogenesis, we determined its genomic structure, and searched for mutations of CDX2 in 49 sporadic colorectal carcinomas and ten hereditary non-polyposis colorectal cancers (HNPCC) without microsatellite instability. None of them exhibited a mutation. We further examined 19 HNPCC carcinomas with microsatellite instability for mutations in a (G)7 repeat site within CDX2. One of them (5.3%) exhibited one G insertion. Loss of heterozygosity was observed in 2 of the 20 (10%) informative sporadic carcinomas, and in one of the three (33.3%) informative HNPCC cancers. These data indicate that CDX2 may play only a minor role in colorectal carcinogenesis.

Amino Acid Sequence↗

Genomic structure of the mouse Ap3b1 gene in normal and pearl mice.

The mouse hypopigmentation mutant pearl is an established model for Hermansky-Pudlak syndrome (HPS), a genetically heterogenous disease with misregulation of the biogenesis/function of melanosomes, lysosomes, and platelet dense granules. The pearl (Ap3b1) gene encodes the beta3A subunit of the AP-3 adaptor complex, which regulates vesicular trafficking. The genomic structure of the normal Ap3b1 gene includes 25 introns and a putative promoter sequence. The original pearl (pe) mutation, which has an unusually high reversion rate on certain strain backgrounds, has been postulated to be caused by insertion of a transposable element. Indeed, the mutation contains a 215-bp partial mouse transposon at the junction point of a large tandem genomic duplication of 6 exons and associated introns. At the cDNA level, three pearl mutations (pearl, pearl-8J, and pearl-9J) are caused by deletions or duplications of a complete exon(s).

Adaptor Protein Complex alpha Subunits↗

Genomic structure and expression of the mouse ESET gene encoding an ERG-associated histone methyltransferase with a SET domain.

ESET (ERG-associated protein with a SET domain, also called SETDB1) is a novel histone methyltransferase that catalyzes methylation of histone H3-lysine 9 (H3-K9). Here we describe the genomic structure and expression of the mouse ESET gene that gives rise to ESET protein and its alternative splicing product. ESET is a 36-kb single copy gene and full-length ESET transcript consisting of 22 exons. The splicing variant retains only the first 12 exons and thus lacks sequences encoding the methyl CpG-binding domain and the catalytic SET domain. The U2 type conserved GT/AG consensus sequence is present at all of the splicing junctions within the ESET gene. The transcription initiation site of the ESET gene was determined by 5'-RACE experiment and by primer extension. The 5'-flanking sequence of the ESET gene does not contain the consensus TATA box. Instead, this ESET promoter region has features such as SP1-binding sites that are typical of housekeeping genes. The ESET promoter was functionally active when tested in transfection and luciferase assay. Full-length ESET transcript appears to be ubiquitously expressed. While the SET domain-deficient splicing variant is present in immortalized cell lines, it is undetectable by RT-PCR in the majority of normal mouse tissues.

Alternative Splicing↗

Genomic structure and chromosome location of the mouse RelA p65 gene (Rela).

The RelA (p65) subunit of transcription factor NF-kappaB plays a critical role in development, and rela(-/-) knockout mice die in utero from massive liver apoptosis. Only partial sequences of the mouse Rela gene are available. We have determined the genomic structure of mouse Rela and promoter, and have mapped the gene to chromosome 19B1-3.

Animals↗