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)

Transcription of vertebrate U6 snRNA genes by RNA polymerase III requires two sequence elements in the proximal promoter region: the PSE (proximal sequence element, found in snRNA promoters transcribed by RNA polymerase II) and the TATA element (found in many mRNA promoters). The locations of the PSE and the TATA box are important determinants for transcriptional start site selection in their respective RNA polymerase II promoters. In vertebrate U6 genes the PSE and the TATA elements are located in approximately the same positions as in the polymerase II transcribed genes, but their respective roles in initiation site selection are unknown. We have analyzed the effects of spacing changes between the PSE and the TATA element, and between the two elements and the normal U6 start site on human U6 gene transcription. The spacing requirement between the two elements is highly stringent, implying a possible interaction between the factors that bind them. Our results discount the possibility that the location of either the PSE or the TATA element, by itself, dictates efficient selection of a transcriptional start site. Instead, we suggest that the two elements form a compound promoter element whose location dictates the start site of transcription from the human U6 gene promoter.
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PMID:The transcriptional start site for a human U6 small nuclear RNA gene is dictated by a compound promoter element consisting of the PSE and the TATA box. 140 5

In this work, we attempted to gain insight into the detailed mechanism allowing correct transcription initiation of U1 snRNA genes by RNA polymerase II. Abolition of the CA motif residing at -1/+1 in the Xenopus U1 gene leads to a loss of the ability of the promoter to direct accurate initiation. A discrete site is selected only if a purine preceded by a pyrimidine is positioned at 58/57 bp downstream of the center of the PSE. The PSE alone is unable to designate a discrete initiation site. Rather, it serves to set the location of an initiation window without discriminating suitable from unsuitable initiation sites. The latter role is devoted to a PyPu sequence positioned at -1/+1. Therefore, it is the concomitant action of the PSE and an essential PyPu positioned at the proper distance from this promoter that specifies correct U1 snRNA transcription initiation by RNA polymerase II.
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PMID:The proximal promoter and the start site cooperate to specify correct U1 snRNA transcription initiation by RNA polymerase II. 157 49

Human mitochondrial RNA processing (MRP) RNA is a 270 nucleotide-long small RNA found as ribonucleoprotein particles. In this study, we isolated four human genomic clones with homology to human MRP RNA. Two of these clones contained one copy each of the real gene coding for human MRP RNA; the other two clones represented a processed psuedogene. The Southern blot with the genomic DNA showed that the haploid human genome contains one copy of real gene and a few pseudogenes for MRP/7-2 RNA. The human MRP RNA is synthesized by RNA polymerase III and the 5' flanking sequences -84 to 1 of MRP RNA gene, containing TATA and PSE-like elements, are required and sufficient for transcription in vitro.
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PMID:5' flanking sequences of human MRP/7-2 RNA gene are required and sufficient for the transcription by RNA polymerase III. 170 54

Transcription factors, required for the basal expression of the mouse U6 gene were identified in extracts from HeLa cells. This gene is transcribed at least four times more efficiently than its human counterpart in extracts from mouse or HeLa cells and hence provides an excellent in vitro system for the identification of transcription factors involved in the basal expression of mammalian U6 genes. At least four separate protein components were found to be required in addition to RNA polymerase III for correct synthesis of U6 RNA in vitro. These correspond to: (i) TFIIIB; (ii) a heat labile activity contained in a protein fraction enriched in TFIID; (iii) an, as yet, uncharacterized component contained in the flow-through upon rechromatography on phosphocellulose, and finally; (iv) a protein specifically binding to the mouse U6 gene promoter and transactivating its expression. Transcription factors IIIA and IIIC are not involved in mammalian U6 transcription in vitro. The U6-specific transcription factor has a molecular mass of approximately 90 +/- 10 kDa. It specifically binds to the U6 gene from bp -42 to -78 on the coding and from bp -37 to -79 on the non-coding strand thereby centrally encompassing the PSE motif of the mouse U6 promoter. The binding activity of this protein is correlated with the efficiency with which the U6 gene is transcribed in vitro, thereby indicating a crucial role of the PSE-binding protein for U6 transcription.
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PMID:Identification of transcription factors required for the expression of mammalian U6 genes in vitro. 186 35

The transcription mode of the Xenopus tRNA(Ser)Sec gene by RNA polymerase III was deciphered by injection of mutant templates into Xenopus oocyte nuclei. tRNA(Ser)Sec represents the paradigm of a new class of RNA polymerase III genes combining tRNA and U snRNA gene regulatory elements. Its promoter is tripartite, constituted by two upstream elements, a PSE and a TATA motif that are interchangeable with those of U6 snRNA genes and an internal box B as in other tRNAs. The B box enables the transcription level dependent on the upstream promoter to be increased. Data obtained indicate that U1 snRNA (Pol II) and tRNA(Ser)Sec (Pol III) genes share at least one transcription factor, implying that the border between transcription systems is less tight than expected.
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PMID:Transcription of the Xenopus laevis selenocysteine tRNA(Ser)Sec gene: a system that combines an internal B box and upstream elements also found in U6 snRNA genes. 200 75

Consensus tRNA gene promoter elements, A and B boxes, were introduced into the coding sequence of a Xenopus U6 gene. Combinations in which A and B boxes were coupled to wild-type or mutant U6 promoters were made. In this way information about both the functions of individual promoter elements and functional relationships between different classes of RNA polymerase III promoter element were obtained. Mutants in which the U6 PSE was non-functional were rescued by the presence of a B box, indicating a degree of functional relationship between these two elements. Moreover, the B box acted to increase the transcriptional activity and competitive strength of the wild-type U6 promoter. In contrast, no evidence was obtained to suggest that a tRNA A box can interact productively with U6 promoter elements in the absence of a B box. Data obtained suggest that the U6 PSE functions as an 'adaptor', being necessary to enable the basal U6 promoter to respond to upstream enhancement. Certain combinations of U6 and tRNA promoter elements are shown to be mutually antagonistic by a mechanism which is likely to involve blockage of transcription initiation. In summary, the U6 and tRNA promoters are shown to consist of functionally related, but distinct, promoter elements whose interactions shed new light on their normal roles in transcription.
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PMID:Positive and negative functional interactions between promoter elements from different classes of RNA polymerase III-transcribed genes. 232 33

The requirements for the formation of a stable transcription complex on the RNA polymerase II-transcribed Xenopus U2 snRNA gene have been analysed in vivo by oocyte microinjection experiments. The two elements of the U2 promoter which are located in the 5' flanking region of the gene, the DSE and the PSE, are shown to be essential but not sufficient for stable complex formation. Two additional elements are required. The first is a short gene-internal sequence; the second is the nucleotide at the normal point of initiation, which must be a purine. If this nucleotide is changed to a pyrimidine the site of initiation is altered and, concomitantly, the transcription complex formed on the mutant template remains unstable. These results suggest that there is a distinct topological requirement for complex formation which may involve an exact stereospecific alignment of RNA polymerase II with transcription factors bound to the promoter. Despite the apparent involvement of RNA polymerase, transcription per se is not required for complex stability.
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PMID:Positionally exact initiation is required for the formation of a stable RNA polymerase II transcription complex in vivo. 320 51

The structure of a Xenopus U6 gene promoter has been investigated. Three regions in the 5'-flanking sequences of the gene that are important for U6 expression are defined. Deletion of the first, between positions -156 and -280 relative to the site of transcription initiation, reduces transcription to roughly 5% of its original level. Deletion of the second, between -60 and -77, abolishes transcription. These regions contain not only functional but also sequence homology to the previously defined distal and proximal sequence elements (DSE and PSE) of the Xenopus U2 promoter, although U2 is transcribed by RNA polymerase II and U6 by RNA polymerase III. Competition experiments show that at least the distal sequence elements of the two promoters bind to a common factor both in vivo and in vitro. Part of the sequence recognized by this factor is the octamer motif (ATG-CAAAT). A sequence similar to the common RNA polymerase II TATA box is also shown to have an effect, albeit minor, on U6 transcription. The U6 coding region contains a good match to the A box, part of all previously characterized RNA polymerase III promoters. Deletion of this region has no apparent effect on the efficiency or accuracy of U6 transcription.
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PMID:A common octamer motif binding protein is involved in the transcription of U6 snRNA by RNA polymerase III and U2 snRNA by RNA polymerase II. 365 9

A minor class of introns with noncanonical splice sites has been identified in both vertebrate and invertebrate genomes. The divergent consensus sequences within these introns suggest that splicing might be via a mechanism distinct from that used by the major class of introns. The low abundance U12 snRNA has been proposed to base pair with the predicted branch site sequence of these minor class introns, probably bulging out an adenosine to act as the nucleophile in the first step of splicing. We have identified homologues of the previously characterized human U12 snRNA in both mouse and chicken, where the minor class of introns has also been found. The U12 sequences that potentially base pair with the putative branch site are invariant. Additional conserved sequences at the 5' end of U12 snRNA could dynamically base pair with U6 snRNA sequences flanking the hexanucleotide ACAGAG to form structures analogous to those of three U2-U6 interactions genetically defined as important in the major class of spliceosome. We have also isolated two human U12 snRNA genes. One gene is functional for transcription of U12 snRNA, whereas the other appears to be a pseudogene. Sequences of the 3' box in both U12 snRNA genes are strikingly similar and bear high resemblance to those of U1 and U2 genes. Upstream elements, including the PSE and the DSE, have been identified and characterized in the functional gene. These features indicate that transcription of U12 snRNA is driven by RNA polymerase II.
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PMID:U12 snRNA in vertebrates: evolutionary conservation of 5' sequences implicated in splicing of pre-mRNAs containing a minor class of introns. 748 23

Fractions obtained from HeLa cell extracts were used to study RNA polymerase III-catalyzed transcription from the human 7SK and mouse U6 RNA promoters in vitro. Although both genes depend on two almost identical core promoter elements (TATA box and PSE), different fractions were required. The 7SK promoter revealed full activity with the phosphocellulose B fraction alone. In contrast, efficient transcription from the U6 promoter depended on the additional presence of the C or D fraction. The analysis of the b1 and b2 subfractions (obtained by DEAE-Sephadex chromatography) revealed that for both promoters the b1 and the phosphocellulose D fraction were mutually interchangeable. However, while both fractions were fully equivalent for the 7SK promoter, the U6 promoter revealed an additional requirement for the C fraction in the presence of the b1 fraction. Since the b1 and the D fractions enclose two different complexes of the TATA-binding protein (TBP), B-TFIID and D-TFIID, our results indicate that functionally these two complexes are responsible for the observed differences in transcription of the 7SK and U6 genes.
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PMID:The seemingly identical 7SK and U6 core promoters depend on different transcription factor complexes. 750 70


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