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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Enhancers stimulate transcription of RNA polymerase II-transcribed genes in an orientation-independent manner and over long distances. This stimulation is known to be associated with an increased polymerase density over the linked gene. However, many aspects of the exact mechanism of remote gene control remain to be elucidated. Based on some reports on RNA polymerase I transcription, we wanted to test whether RNA polymerase II enters at the enhancer and from there proceeds towards the promoter while synthesizing unstable transcripts ("scanning/readthrough transcription" model). For this, we have inserted a complete terminator region from the mouse beta-globinmaj gene between the SV40 enhancer and the rabbit beta-globin promoter. In contrast to what the model predicts, insertion of the terminator had no affect on remote enhancer action. Furthermore, we have determined the RNA polymerase density over the spacer DNA between enhancer and promoter, and over the reporter gene, by means of the so-called run-on transcription assay. We find very low transcription of the spacer, but high transcription of the globin reporter gene. Thus, our data are not consistent with a scanning/readthrough transcription mechanism where RNA polymerase II would move from the enhancer to the promoter while transcribing the intervening spacer DNA. These and other findings are compatible with a model where enhancer and promoter are brought into close proximity, perhaps with concomitant looping out of the intervening DNA.
Somat Cell Mol Genet 1990 Jul
PMID:A transcriptional terminator between enhancer and promoter does not affect remote transcriptional control. 221 23

The rpoA gene of Escherichia coli encodes the alpha subunit of the DNA-dependent RNA polymerase. Two mutant alleles, rpoA101 and rpoA112, both of which produce RNA polymerase with altered thermostability and reduced fidelity of transcription in vitro (Ishihama et al. (1980) J. Mol. Biol. 137, 137-150), have been analyzed in details. The mutations were found to be responsible for the temperature-sensitive growth by complementation test using a rpoA-expression plasmid. Each mutant allele was amplified from total cell DNA by PCR (polymerase chain reaction) and directly sequenced. Both the mutant rpoA genes were found to carry a single base transition which leads to a substitution of Cys for Arg at the position 191 (rpoA101) or 45 (rpoA112), respectively. Since the rpoA112 mutation causes the defect in RNA polymerase assembly (Kawakami & Ishihama (1980) Biochemistry 19, 3491-3495), the amino-terminal region of alpha including the position 45 was considered to play an important role in subunit assembly.
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PMID:Sequence analysis of two temperature-sensitive mutations in the alpha subunit gene (rpoA) of Escherichia coli RNA polymerase. 223 79

NIH 3T3 cells infected with Moloney murine leukemia virus (MoMLV) express high levels of virus-specific RNA. To inhibit replication of the virus, we stably introduced chimeric tRNA genes encoding antisense templates into NIH 3T3 cells via a retroviral vector. Efficient expression of hybrid tRNA-MoMLV antisense transcripts and inhibition of MoMLV replication were dependent on the use of a particular type of retroviral vector, the double-copy vector, in which the chimeric tRNA gene was inserted in the 3' long terminal repeat. MoMLV replication was inhibited up to 97% in cells expressing antisense RNA corresponding to the gag gene and less than twofold in cells expressing antisense RNA corresponding to the pol gene. RNA and protein analyses suggest that inhibition was exerted at the level of translation. These results suggest that RNA polymerase III-based antisense inhibition systems can be used to inhibit highly expressed viral genes and render cells resistant to viral replication via intracellular immunization strategies.
Mol Cell Biol 1990 Dec
PMID:Expression of chimeric tRNA-driven antisense transcripts renders NIH 3T3 cells highly resistant to Moloney murine leukemia virus replication. 224 70

A Schizosaccharomyces pombe U6 small nuclear RNA gene containing an intron has been described. We find that the S. pombe U6 gene is transcribed in a human (HeLa) cell S100 extract with an alpha-amanitin sensitivity characteristic of RNA polymerase III. The S. pombe U6 gene is also transcribed after transfection into human cells. The transcription of vertebrate U6 RNA genes by RNA polymerase III does not require intragenic control elements. The intron of the S. pombe U6 gene disrupts a "box A"-like intragenic sequence that is typically an RNA polymerase III transcription control element. This, together with the transcription of the S. pombe U6 gene by human RNA polymerase III, suggests that it is recognized by human U6 gene-specific transcription machinery.
J Mol Biol 1990 Jan 05
PMID:An intron-containing Schizosaccharomyces pombe U6 RNA gene can be transcribed by human RNA polymerase III. 229 73

A new affinity chromatographic procedure for the separation of transcriptionally active nucleosomes has been used to study the changes that take place in chromatin structure along the c-fos and c-myc genes when RNA synthesis is inhibited. Mercury-affinity chromatography separates the sulfhydryl-reactive nucleosomes of transcriptionally active genes from the compactly beaded, non-reactive nucleosomes of transcriptionally inert DNA sequences. The new procedure also discriminates between nucleosomes that have "unfolded" to reveal the previously shielded SH groups of histone H3 and nucleosomes that bind to the mercury column because of their association with thiol-containing non-histone proteins located in the transcription unit. Both classes of Hg-bound nucleosomes contain the c-fos and c-myc sequences, but only when they are being transcribed. We compared the effects of alpha-amanitin and actinomycin D on the transcription of c-fos and c-myc with the effects of each inhibitor on the distribution of the corresponding oncogenic DNA sequences in the chromatographically separated nucleosome fractions. It was found that the inhibition of RNA polymerase II by alpha-amanitin (added at the peaks of c-fos or c-myc expression in serum-stimulated BALB/c 3T3 cells) resulted in a rapid loss of affinity of the oncogene-containing nucleosomes for the mercury column. There was no corresponding effect on the mercury-binding properties of nucleosomes containing 28 S ribosomal gene sequences, which continue to be transcribed by amanitin-resistant RNA polymerase I. Therefore, the binding of the c-fos and c-myc nucleosomes to the mercury column seems to depend upon reversible structural changes associated with their transcription. Surprisingly, there was no corresponding loss of affinity of the c-fos and c-myc nucleosomes for the mercury column when actinomycin D was employed to inhibit RNA synthesis, despite the fact that transcription of both genes had been arrested abruptly. Measurements of [3H]actinomycin D binding show its preferential intercalation into the transcriptionally active nucleosomes. We suggest that the intercalation of actinomycin D into the DNA of active nucleosomes can lock the transcription complex into an "unfolded" but potentially active configuration. This was confirmed by run-off transcription assays showing a restoration of c-fos and c-myc RNA synthesis when actinomycin D was displaced by proflavine.
J Mol Biol 1990 Apr 05
PMID:Reversible and irreversible changes in nucleosome structure along the c-fos and c-myc oncogenes following inhibition of transcription. 232 30

We describe a partially fractionated in vitro transcription system from Xenopus laevis for the assay of transcription termination by RNA polymerase I. Termination in vitro was found to require a specific terminator sequence in the DNA and a DNA-binding protein fraction that produces a footprint over the terminator sequence.
Mol Cell Biol 1990 Jun
PMID:A DNA-binding protein is required for termination of transcription by RNA polymerase I in Xenopus laevis. 234 63

The protein components that direct and activate accurate transcription by rat RNA polymerase I were studied in extracts of Novikoff hepatoma ascites cells. A minimum of at least two components, besides RNA polymerase I, that are necessary for efficient utilization of templates were identified. The first factor, rat SL-1, is required for species-specific recognition of the rat RNA polymerase I promoter and may be sufficient to direct transcription by pure RNA polymerase I. Rat SL-1 directed the transcription of templates deleted to -31, the 5' boundary of the core promoter element (+1 being the transcription initiation site). The second factor, rUBF, increased the efficiency of template utilization. Transcription of deletion mutants indicated that the 5' boundary of the domain required for rUBF lay between -137 and -127. Experiments using block substitution mutants confirmed and extended these observations. Transcription experiments using those mutants demonstrated that two regions within the upstream promoter element were required for optimal levels of transcription in vitro. The first region was centered on nucleotides -129 and -124. The 5' boundary of the second domain mapped to between nucleotides -106 and -101. DNase footprint experiments using highly purified rUBF indicated that rUBF bound between -130 and -50. However, mutation of nucleotides -129 and -124 did not affect the rUBF footprint. These results indicate that basal levels of transcription by RNA polymerase I may require only SL-1 and the core promoter element. However, higher transcription levels are mediated by additional interactions of rUBF, and possibly SL-1, bound to distal promoter elements.
Mol Cell Biol 1990 Jun
PMID:Characterization of factors that direct transcription of rat ribosomal DNA. 234 70

The complete nucleotide (nt) sequence of the rat nuc gene encoding nucleolin, the major nucleolar-specific protein in eukaryotic exponentially growing cells, is compared with the corresponding locus recently characterized in mouse. [Bourbon et al., J. Mol. Biol. 200 (1988) 627-638]. In both murine species the genomic organization has been strikingly conserved during evolution, i.e., the coding region extends over 9 kb and is split into 14 exons, encoding a 712-amino acid protein. Moreover, all the exon-intron junction positions were strictly maintained during evolution. More unexpectedly, this analysis revealed that several introns contain highly conserved sequence elements of about 120 nt. The nt sequence of the homologous locus isolated from a Chinese hamster genomic clone established that these regions were under unusually high selective constraints (84-96% identity between the hamster and murine nuc genes) and, although they do not contain open reading frames, they surprisingly appear to be more conserved than most of the exons, suggesting that they play an important role. Such an element of 130 nt presents features of known genes transcribed by RNA polymerase III. Furthermore, in the rat nuc pre-mRNA the 5'- and 3'-end regions of the last intron are fully complementary over 16 nt, and so are predicted to be included in a prominent stem structure. Moreover, an homologous RNA stem structure can be derived from the mouse sequence, including two compensatory nt changes. As the secondary structure would occlude the canonical sequences required for the proper excision of this intron in both murine species, this remarkable finding could be relevant to the regulation of the nuc gene expression at the RNA processing level.
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PMID:Nucleolin gene organization in rodents: highly conserved sequences within three of the 13 introns. 234 93

Rat cells contain a DNA-binding polymerase I transcription factor, rUBF, with properties similar to UBF homologs that have been purified from both human (hUBF) and frog (xUBF) cells. In this note we report the affinity purification of rUBF to apparent homogeneity and show that UBFs from both rat and frog have identical footprinting characteristics on templates from either species. Furthermore, xUBF was able to stimulate transcription from rat RNA polymerase I promoters in a partially fractionated rat extract that was UBF dependent. These results strengthen the conclusion that all vertebrate cells contain a UBF homolog whose DNA-binding specificity and function have been strongly conserved.
Mol Cell Biol 1990 Jul
PMID:rUBF, an RNA polymerase I transcription factor from rats, produces DNase I footprints identical to those produced by xUBF, its homolog from frogs. 235 24

B2 genes are short repeated sequences which are transcribed by RNA polymerase III. Abundant transcripts accumulate in embryonic and transformed cells, but transcripts are rare or absent from normal differentiated cell types. During retinoic acid-induced differentiation of P19 embryonal carcinoma cells, an early transient increase in B2 RNA levels is followed by a rapid drop in expression. The marked changes in B2 RNA levels are most likely due to transcriptional modulation since B2 RNA stabilities are unaffected by differentiation. At least four short-lived B2 RNAs with apparent lengths of 150, 180, 240, and 500 nucleotides were characterized. The two larger RNAs are polyadenylated and are more stable in cells. A cDNA of a B2 gene was isolated which was over 99% identical to the consensus sequence. This B2 cDNA can be transcribed in human cells and yields at least two distinct transcripts. We propose a model for B2 RNA metabolism which describes transcription, posttranscriptional modification and processing, and nucleocytoplasmic transport.
Mol Cell Biol 1990 Aug
PMID:Synthesis and processing of small B2 transcripts in mouse embryonal carcinoma cells. 237 Aug 62


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