Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The TATA-box-binding protein TBP exists in the cell complexed with different sets of TBP-associated factors (TAFs). In general, each of these TBP-TAF complexes is dedicated to transcription by a single RNA polymerase. Thus, SL1, TFIID and TFIIIB are required for transcription by polymerases I, II and III, respectively. Here we characterize a fourth TBP-TAF complex called SNAPc. Unlike the other TBP-TAF complexes, SNAPc is implicated in transcription by two types of polymerases; it is required for transcription of both the RNA polymerase II and III small-nuclear RNA genes and binds specifically to the proximal sequence element PSE, a non-TATA-box basal promoter element common to these two types of genes. In addition to TBP, SNAPc is composed of at least three TAFs, SNAP43, SNAP45 and SNAP50. The predicted amino-acid sequence of SNAP43 reveals that it corresponds to a new protein.
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PMID:A TBP-TAF complex required for transcription of human snRNA genes by RNA polymerase II and III. 771 7

The human RNA polymerase II and III snRNA promoters share a common basal element, the proximal sequence element (PSE), which is recognized by a complex we refer to as the snRNA-activating protein complex (SNAPc). Biochemical purifications suggest that SNAPc is composed of at least four polypeptides of 43, 45, 50 and 190 kDa, as well as variable amounts of the TATA box binding protein, TBP. cDNAs encoding the 43 and 45 kDa subunits, SNAP43 and SNAP45, have been isolated, but there is no evidence that either of these subunits contacts DNA. Here we report the isolation of cDNAs encoding the 50 kDa subunit of SNAPc, SNAP50. The open reading frame predicts a 411 amino acid protein, which contains two potential zinc finger motifs. Depletions with anti-SNAP50 antibodies inhibit RNA polymerase II and III snRNA gene transcription in vitro. SNAP50 interacts with SNAP43 in co-immunoprecipitation experiments, but not with SNAP45 or TBP. UV cross-linking experiments suggest that SNAP50 contacts DNA in the SNAP complex. These results are consistent with the same core SNAP complex recognizing the PSEs of RNA polymerase II and III snRNA promoters, and provide an initial view of the architecture of the SNAP complex.
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PMID:Cloning and characterization of SNAP50, a subunit of the snRNA-activating protein complex SNAPc. 900 88

The human RNA polymerase II and III snRNA promoters have similar enhancers, the distal sequence elements (DSEs), and similar basal promoter elements, the proximal sequence elements (PSEs). The DSE, which contains an octamer motif, binds broadly expressed activator Oct-1. The PSE binds a multiprotein complex referred to as SNAPc or PTF. On DNAs containing both an octamer site and a PSE, Oct-1 and SNAPc bind cooperatively. SNAPc consists of at least four stably associated subunits, SNAP43, SNAP45, SNAP50, and SNAP190. None of the three small subunits, which have all been cloned, can bind to the PSE on their own. Here we report the isolation of cDNAs corresponding to the largest subunit of SNAPc, SNAP190. SNAP190 contains an unusual Myb DNA binding domain consisting of four complete repeats (Ra to Rd) and a half repeat (Rh). A truncated protein consisting of the last two SNAP190 Myb repeats, Rc and Rd, can bind to the PSE, suggesting that the SNAP190 Myb domain contributes to recognition of the PSE by the SNAP complex. SNAP190 is required for snRNA gene transcription by both RNA polymerases II and III and interacts with SNAP45. In addition, SNAP190 interacts with Oct-1. Together, these results suggest that the largest subunit of the SNAP complex is involved in direct recognition of the PSE and is a target for the Oct-1 activator. They also provide an example of a basal transcription factor containing a Myb DNA binding domain.
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PMID:The large subunit of basal transcription factor SNAPc is a Myb domain protein that interacts with Oct-1. 941 84

The basal transcription factor SNAPc binds to the PSE, a core element in the RNA polymerase II and III human snRNA promoters. SNAPc contains at least four subunits, but it has not been possible to assemble a fully defined recombinant SNAPc. Here we reconstitute SNAPc from five recombinant subunits, SNAP43, SNAP45, SNAP50, SNAP190, and a newly identified subunit, SNAP19. This recombinant complex binds specifically to the PSE and directs both RNA polymerase II and III snRNA gene transcription. Thus, the same core SNAPc nucleates the assembly of two classes of initiation complexes.
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PMID:SNAP19 mediates the assembly of a functional core promoter complex (SNAPc) shared by RNA polymerases II and III. 973 65

The nucleation of RNA polymerases I-III transcription complexes is usually directed by distinct multisubunit factors. In the case of the human RNA polymerase II and III small nuclear RNA (snRNA) genes, whose core promoters consist of a proximal sequence element (PSE) and a PSE combined with a TATA box, respectively, the same multisubunit complex is involved in the establishment of RNA polymerase II and III initiation complexes. This factor, the snRNA-activating protein complex or SNAP(c), binds to the PSE of both types of promoters and contains five types of subunits, SNAP190, SNAP50, SNAP45, SNAP43, and SNAP19. SNAP(c) binds cooperatively with both Oct-1, an activator of snRNA promoters, and in the RNA polymerase III snRNA promoters, with TATA-binding protein, which binds to the TATA box located downstream of the PSE. Here we have defined subunit domains required for SNAP(c) subunit-subunit association, and we show that complexes containing little more than the domains mapped here as required for subunit-subunit contacts bind specifically to the PSE. These data provide a detailed map of the subunit-subunit interactions within a multifunctional basal transcription complex.
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PMID:A map of protein-protein contacts within the small nuclear RNA-activating protein complex SNAPc. 1105 76

The retinoblastoma protein (RB) represses RNA polymerase III transcription effectively both in vivo and in vitro. Here we demonstrate that the general transcription factors snRNA-activating protein complex (SNAP(c)) and TATA binding protein (TBP) are important for RB repression of human U6 snRNA gene transcription by RNA polymerase III. RB is associated with SNAP(c) as detected by both coimmunoprecipitation of endogenous RB with SNAP(c) and cofractionation of RB and SNAP(c) during chromatographic purification. RB also interacts with two SNAP(c) subunits, SNAP43 and SNAP50. TBP or a combination of TBP and SNAP(c) restores efficient U6 transcription from RB-treated extracts, indicating that TBP is also involved in RB regulation. In contrast, the TBP-containing complex TFIIIB restores adenovirus VAI but not human U6 transcription in RB-treated extracts, suggesting that TFIIIB is important for RB regulation of tRNA-like genes. These results suggest that different classes of RNA polymerase III-transcribed genes have distinct general transcription factor requirements for repression by RB.
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PMID:The retinoblastoma tumor suppressor protein targets distinct general transcription factors to regulate RNA polymerase III gene expression. 1109 70

Human U6 small nuclear RNA (snRNA) gene transcription by RNA polymerase III requires cooperative promoter binding involving the snRNA-activating protein complex (SNAP(c)) and the TATA-box binding protein (TBP). To investigate the role of SNAP(c) for TBP function at U6 promoters, TBP recruitment assays were performed using full-length TBP and a mini-SNAP(c) containing SNAP43, SNAP50, and a truncated SNAP190. Mini-SNAP(c) efficiently recruits TBP to the U6 TATA box, and two SNAP(c) subunits, SNAP43 and SNAP190, directly interact with the TBP DNA binding domain. Truncated SNAP190 containing only the Myb DNA binding domain is sufficient for TBP recruitment to the TATA box. Therefore, the SNAP190 Myb domain functions both to specifically recognize the proximal sequence element present in the core promoters of human snRNA genes and to stimulate TBP recognition of the neighboring TATA box present in human U6 snRNA promoters. The SNAP190 Myb domain also stimulates complex assembly with TBP and Brf2, a subunit of a snRNA-specific TFIIIB complex. Thus, interactions between the DNA binding domains of SNAP190 and TBP at juxtaposed promoter elements define the assembly of a RNA polymerase III-specific preinitiation complex.
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PMID:The small nuclear RNA-activating protein 190 Myb DNA binding domain stimulates TATA box-binding protein-TATA box recognition. 1262 Oct 23

In the protist parasite Trypanosoma brucei, the small nuclear spliced leader (SL) RNA and the large rRNAs are key molecules for mRNA maturation and protein synthesis, respectively. The SL RNA gene (SLRNA) promoter recruits RNA polymerase II and consists of a bipartite upstream sequence element (USE) and an element close to the transcription initiation site. Here, we analyzed the distal part of the ribosomal (RRNA) promoter and identified two sequence blocks which, in reverse orientation, closely resemble the SLRNA USE by both sequence and spacing. A detailed mutational analysis revealed that the ribosomal (r)USE is essential for efficient RRNA transcription in vivo and that it functions in an orientation-dependent manner. Moreover, we showed that USE and rUSE are functionally interchangeable and that rUSE stably interacted with an essential factor of SLRNA transcription. Finally, we demonstrated that the T.brucei homolog of the recently characterized transcription factor p57 of the related organism Leptomonas seymouri specifically bound to USE and rUSE. Since p57 and its T.brucei counterpart are homologous to SNAP50, a component of the human small nuclear RNA gene activation protein complex (SNAPc), both SLRNA and RRNA transcription in T.brucei may depend on a SNAPc-like transcription factor.
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PMID:The Trypanosoma brucei spliced leader RNA and rRNA gene promoters have interchangeable TbSNAP50-binding elements. 1475 34

The small nuclear RNA (snRNA)-activating protein complex (SNAP(c)) is a multi-subunit transcription factor characterized in humans and Drosophila melanogaster. It binds to an upstream sequence element (USE) of snRNA gene promoters and activates both RNA polymerase (pol) II and III-mediated transcription of snRNA genes. The first identified and partially characterized transcription factor in a trypanosomatid organism appears to be a SNAP(c) homologue. It was identified in Leptomonas seymouri and shown to specifically interact with the USE of the RNA pol II-transcribed spliced leader (SL) RNA gene. Recently, chromatin immunoprecipitation and a gel shift assay suggested that L. seymouri SNAP(c) also interacts with RNA pol III-transcribed U2 and U6 snRNA genes. Previously, we have characterized and epitope-tagged the Trypanosoma brucei homologue of the SNAP50 subunit. Here, we show by in vitro transcription competition and promoter pull-down assays that TbSNAP50 binds to the SL RNA gene promoter and parasite-specifically to the ribosomal RNA gene promoter. Conversely, we did not detect binding of the factor to U2 and U6 snRNA gene sequences. Since U snRNA gene promoters are structurally conserved among trypanosomatids, our findings contrast those obtained in L. seymouri and suggest that trypanosomatid SNAP(c) is not involved in RNA pol III-mediated transcription of U snRNA genes.
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PMID:Failure to detect binding of Trypanosoma brucei SNAPc to U2 and U6 snRNA gene sequences by in vitro transcription competition and pull-down assays. 1538 99

Human small nuclear (sn) RNA genes are transcribed by either RNA polymerase II or III depending upon the arrangement of their core promoter elements. Regardless of polymerase specificity, these genes share a requirement for a general transcription factor called the snRNA activating protein complex or SNAP(C). This multi-subunit complex recognizes the proximal sequence element (PSE) commonly found in the upstream promoters of human snRNA genes. SNAP(C) consists of five subunits: SNAP190, SNAP50, SNAP45, SNAP43, and SNAP19. Previous studies have shown that a partial SNAP(C) composed of SNAP190 (1-514), SNAP50, and SNAP43 expressed in baculovirus is capable of PSE-specific DNA binding and transcription of human snRNA genes by RNA polymerases II and III. Expression in a baculovirus system yields active complex but the concentration of such material is insufficient for many bio-analytical methods. Herein, we describe the co-expression in Escherichia coli of a partial SNAP(C) containing SNAP190 (1-505), SNAP50, SNAP43, and SNAP19. The co-expressed complex binds DNA specifically and recruits TBP to U6 promoter DNA. Importantly, this partial complex functions in reconstituted transcription of both human U1 and U6 snRNA genes by RNA polymerases II and III, respectively. This co-expression system will facilitate the functional characterization of this unusual multi-protein transcription factor that plays an important early role for transcription by two different polymerases.
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PMID:Co-expression of multiple subunits enables recombinant SNAPC assembly and function for transcription by human RNA polymerases II and III. 1660 80


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