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)

Human ribosomal RNA synthesis by RNA polymerase I requires the activator UBF and the promoter selectivity factor SL1, which consists of the TATA binding protein (TBP) and three associated subunits, TAFI110, TAFI63, and TAFI48. Here it is shown that both TAFI110 and TAFI63 contact the promoter, whereas TAFI48 serves as a target for interaction with UBF and is required to form a transcriptionally active SL1 complex responsive to UBF in vitro. TAFI48 also alters the ability of TBP to interact with TATA box elements, and the resulting complex fails to support transcription by RNA polymerase II. Thus, TAFI48 may function both as a target to mediate UBF activation and as a class-specific promoter selectivity factor.
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PMID:Coactivator and promoter-selective properties of RNA polymerase I TAFs. 749

DNA-dependent protein kinase (DNA-PK) is a nuclear enzyme that phosphorylates several transcription factors, but its cellular function has not been elucidated. Here I show that DNA-PK strongly inhibits promoter-directed transcription initiation by Xenopus RNA polymerase I in vitro. The repression is due to protein phosphorylation, since it is relieved by 6-dimethylaminopurine, an inhibitor of protein kinases. DNA-PK inhibits transcription from both linear and circular templates, but the repression is more efficient on linear templates. DNA-PK has no effect on promoter-directed transcription by RNA polymerases II and III. Partial fractionation of the in vitro transcription system shows that a protein fraction containing transcription factor Rib1, the Xenopus equivalent of human SL1, mediates the repression of transcription by DNA-PK. The present data suggest a role for DNA-PK in down-regulating ribosomal gene transcription.
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PMID:DNA-dependent protein kinase specifically represses promoter-directed transcription initiation by RNA polymerase I. 770 51

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

RNA polymerase I and II transcription factors SL1 and TFIID, respectively, are composed of the TATA-binding protein (TBP) and a set of TBP-associated factors (TAFs) responsible for promoter recognition. How the universal transcription factor TBP becomes committed to a TFIID or SL1 complex has not been known. Complementary DNAs encoding each of the three TAFIs that are integral components of SL1 have not been isolated. Analysis of subunit interactions indicated that the three TAFIs can bind individually and specifically to TBP. In addition, these TAFIs interact with each other to form a stable TBP-TAF complex. When TBP was bound first by either TAFI110, 63, or 48, subunits of TFIID such as TAFII250 and 150 did not bind TBP. Conversely, if TBP first formed a complex with TAFII250 or 150, the subunits of SL1 did not bind TBP. These results suggest that a mutually exclusive binding specificity for TBP intrinsic to SL1 and TFIID subunits directs the formation of promoter- and RNA polymerase-selective TBP-TAF complexes.
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PMID:Reconstitution of transcription factor SL1: exclusive binding of TBP by SL1 or TFIID subunits. 780 Nov 23

Initiation of ribosomal RNA synthesis by RNA polymerase I requires the promoter selectivity factor SL1, which consists of the TATA-binding protein, TBP, and three associated factors, TAFIS 110, 63, and 48. Here the in vivo and in vitro assembly of functional SL1 complexes from recombinant TAFIS and TBP are reported. Complexes containing TBP and all three TAFIS were as active in supporting transcription from the human ribosomal RNA gene promoter as endogenous SL1, whereas partial complexes without TBP did not efficiently direct transcription in vitro. These results suggest that TAFIS 110, 63, and 48, together with TBP, are necessary and sufficient to reconstitute a transcriptionally active SL1 complex.
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PMID:Assembly of transcriptionally active RNA polymerase I initiation factor SL1 from recombinant subunits. 780 Nov 30

Basic mechanisms of transcription initiation are conserved from yeast to man. However, in contrast to genes transcribed by RNA polymerases II and III, ribosomal gene transcription by RNA polymerase I (Pol I) is species-specific. Promoter selectivity is mediated by SL1/TIF-IB, a multiprotein complex containing the TATA-binding protein (TBP) and TBP-associated factors (TAFs) which bind to DNA and nucleate the assembly of initiation complexes. Using a human cell line that expresses epitope-tagged yeast TBP, we have isolated a chimeric complex consisting of yeast TBP and human TAFs which faithfully promotes human rDNA transcription in vitro. This result argues that specific interactions between TBP and Pol I-specific TAFs have been evolutionarily conserved between distant species. In addition, this finding also underscores the importance of TAFs in determining promoter selectivity of Pol I.
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PMID:Yeast TBP can replace its human homologue in the RNA polymerase I-specific multisubunit factor SL1. 796 4

The accurate transcription of human rRNA genes by RNA polymerase I requires two transcription factors, upstream binding factor (UBF) and promoter selectivity factor (SL1). Human SL1 (hSL1) is a multisubunit complex, one of whose components is TATA box-binding protein (TBP). hSL1 binds to the core region of the rRNA promoter, but does so inefficiently in the absence of human UBF (hUBF). hUBF interacts with the upstream control element of the rRNA promoter and facilitates binding of hSL1. The molecular basis by which hUBF increases binding of hSL1 remains to be elucidated. In this report, we use an immobilized protein binding assay to identify and purify a 95-kDa TBP-binding polypeptide. Microsequence analysis reveals that the 95-kDa TBP-binding protein is hUBF. We show that hUBF is stably associated with TBP and is present in large TBP-containing complexes. Our results indicate that the cooperative binding of hUBF and hSL1 on the rRNA promoter is mediated by direct interaction between hUBF and TBP. We also provide evidence that hUBF associates with TFIID, a TBP-containing RNA polymerase II transcription factor.
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PMID:The RNA polymerase I transcription factor, upstream binding factor, interacts directly with the TATA box-binding protein. 798 18

Factor C* is the component of the RNA polymerase I holoenzyme (factor C) that allows specific transcriptional initiation on a factor D (SL1)- and UBF-activated rRNA gene promoter. The in vitro transcriptional capacity of a preincubated rDNA promoter complex becomes exhausted very rapidly upon initiation of transcription. This is due to the rapid depletion of C* activity. In contrast, C* activity is not unstable in the absence of transcription, even in the presence of nucleoside triphosphates (NTPs). By using 3'dNTPs to specifically halt elongation, C* is seen to remain active through transcription complex assembly, initiation, and the first approximately 37 nucleotides of elongation, but it is inactivated before synthesis proceeds beyond approximately 40 nucleotides. When elongation is halted before this critical distance, the C* remains active and on that template complex, greatly extending the kinetics of transcription and generating manyfold more transcripts than would have been synthesized if elongation had proceeded past the critical distance where C* is inactivated. In complementary in vivo analysis under conditions where C* activity is not replenished, C* activity becomes depleted from cells, but this also occurs only when there is ongoing rDNA transcription. Thus, both in vitro and in vivo, the specific initiation-conferring component of the RNA polymerase I holoenzyme is used stoichiometrically in the transcription process.
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PMID:Factor C*, the specific initiation component of the mouse RNA polymerase I holoenzyme, is inactivated early in the transcription process. 800 94

Unlike genes transcribed by RNA polymerases II and III, transcription by RNA polymerase I is highly species-specific. Ribosomal promoter selectivity is brought about by a multisubunit transcription factor (SL1/TIF-IB) which consists of the TATA-binding protein (TBP) and three TBP-associated factors (TAFs). To determine the basis for the inability of SL1/TIF-IB to recognize heterologous rDNA, the transcriptional properties and the subunit composition of the murine and the human factor, as well as a chimeric complex containing epitope-tagged human TBP and murine TAFs, have been compared. We show that TBP can be exchanged between the human and mouse factor indicating that the variable N-terminal domain of TBP does not play a significant role in rDNA promoter selectivity. Instead, DNA binding is brought about by the TAFs. UV crosslinking experiments demonstrate that binding to the ribosomal gene promoter is mediated by two TAFs (TAFI48 and TAFI68) which have the same electrophoretic mobility in the human and mouse factor. The largest TAF is different in both species and is suggested to play a role in the species-specific assembly of productive preinitiation complexes. Thus, evolutionary changes of rDNA promoter sequences have been accompanied by changes in specific TAFs.
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PMID:TBP-associated factors interact with DNA and govern species specificity of RNA polymerase I transcription. 801 60

The human ribosomal RNA polymerase (Pol) I promoter selectivity factor SL1 is a complex consisting of the TATA binding protein (TBP) and three TBP-associated factors (TAFs). We have investigated which elements of TBP are involved in the assembly of Pol I-specific TBP-TAF complexes by comparing SL1 isolated from two human cell lines, one expressing epitope-tagged full-length TBP and another expressing a deletion of nearly the entire N-terminal domain (e delta NTBP). We have immunopurified epitope-tagged full-length TBP- and e delta NTBP-TAF complexes and show that e delta NTBP reconstitutes SL1 activity almost as well as full-length TBP. Moreover, e delta NTBP is shown to be associated with all three Pol I-specific TAFs. Thus, the core of TBP alone is sufficient for the correct assembly of the Pol I-specific TBP-TAF complex, and the variable N-terminal region of human TBP is not required for transcriptional activity. We also demonstrate by an in vitro protein-protein interaction assay that TBP directly interacts with the smallest TAF, TAFI48.
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PMID:The conserved core domain of the human TATA binding protein is sufficient to assemble the multisubunit RNA polymerase I-specific transcription factor SL1. 805 85


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