Pol I transcription: Which comes first, the end or the beginning?

Baker, Steven M.; Platt, Terry

doi:10.1016/0092-8674(86)90795-6

Cited by 56 publications

(28 citation statements)

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“…3D, compare lanes 2 and 3). This result confirms the absence of any significant stimulation of transcription of a rRNA gene by hypothetical cis elements further "upstream" of SmaI site (Ϫ209) or by transcription of the upstream rRNA gene as proposed by earlier investigators ("polymerase hand-over model" [1,36,42; see also the Discussion]).…”

Section: Resultssupporting

confidence: 91%

“…1Aii, iii, and iv, respectively) were obtained in this way. We note that the site of integration in NOY2047 is ϳ500 bp from the telomere repeats ([TG [1][2][3] ] n -end) and, because of the presence of the ϳ1.0-kb HIS3 gene, the integrated rDNA* repeat is located ϳ1.5 kb from the telomere repeats. (An integration site near TEL VI-R was selected because of the absence of YЈ element at this chromosome end [41].)…”

Section: Methodsmentioning

confidence: 99%

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Expression of rRNA Genes and Nucleolus Formation at Ectopic Chromosomal Sites in the Yeast Saccharomyces cerevisiae

Oakes

Johzuka

et al. 2006

Molecular and Cellular Biology

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We constructed yeast strains in which rRNA gene repeats are integrated at ectopic sites in the presence or absence of the native nucleolus. At all three ectopic sites analyzed, near centromere CEN5, near the telomere of chromosome VI-R, and in middle of chromosome V-R (mid-V-R), a functional nucleolus was formed, and no difference in the expression of rRNA genes was observed. When two ribosomal DNA (rDNA) arrays are present, one native and the other ectopic, there is codominance in polymerase I (Pol I) transcription. We also examined the expression of a single rDNA repeat integrated into ectopic loci in strains with or without the native RDN1 locus. In a strain with reduced rRNA gene copies at RDN1 (ϳ40 copies), the expression of a single rRNA gene copy near the telomere was significantly reduced relative to the other ectopic sites, suggesting a less-efficient recruitment of the Pol I machinery from the RDN1 locus. In addition, we found a single rRNA gene at mid-V-R was as active as that within the 40-copy RDN1. Combined with the results of activity analysis of a single versus two tandem copies at CEN5, we conclude that tandem repetition is not required for efficient rRNA gene transcription.

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Section: Resultssupporting

confidence: 91%

Section: Methodsmentioning

confidence: 99%

Expression of rRNA Genes and Nucleolus Formation at Ectopic Chromosomal Sites in the Yeast Saccharomyces cerevisiae

Oakes

Johzuka

et al. 2006

Molecular and Cellular Biology

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“…When mini-RNA genes are transcripted in vivo or in vitro (16,22,36), more RNAs are correctly initiated when an upstream terminator is present that when it is absent. Two mechanisms have been proposed to explain why the upstream terminator might enhance the level of Pol I initiation: (i) the terminator could increase the local concentration of Pol I by virtue of the fact that termination occurred within a few hundred nucleotides of the initiation site (1,12,28,36,37), or (ii) as has been shown, read-in transcription dissociates transcription initiation factors from the Pol I promoter (4). Thus, the upstream terminator would facilitate initiation by allowing the initiation complex to bind more stably.…”

Section: Discussionmentioning

confidence: 99%

“…Cellular RNA (0.1 to (ii) High-specific-activity RNA. High-specific-activity RNAs were transcribed as described above except that 1 terminated at the correct site, with the remainder extending to at least +650, which was the extent of complementarity with the probe.…”

Section: Methodsmentioning

confidence: 99%

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Analysis of pre-rRNAs in heat-shocked HeLa cells allows identification of the upstream termination site of human polymerase I transcription.

Parker¹,

Bond²

1989

Mol. Cell. Biol.

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Human rRNA precursors from normal or stressed HeLa cells were studied by Si nuclease mapping of unlabeled RNA and by antisense RNase mapping of RNA from cells that had been labeled in vivo with[32p]PO4. Heating cells to 43°C decreased the amount of newly synthesized rRNA to less than 5% of the control level and led to greater than 95% inhibition of transcription termination at a region 355 to 362 nucleotides downstream of the 3' end of 28S rRNA, with readthrough continuing into the next transcription unit. Heating of cells to 42°C led to 60% inhibition of termination at this site; 50% of transcripts that extended into the nontranscribed spacer ended in a region 200 to 210 nucleotides upstream of the polymerase I (Pol I) initiation site. This is presumed to be the human upstream transcription termination site because of the absence of RNAs with a 5' end corresponding to this region, the location relative to the Pol I initiation site (which is similar to the location of upstream terminators in other species), and the fact that it is 15 to 25 nucleotides upstream of the sequence GGGTTGACC, which has an 8-of-9 base identity with the sequence 3' of the downstream termination site. Surprisingly, treatment of cells with sodium arsenite, which also leads to the induction of a stress response, did not inhibit termination. Pol I initiation was decreased to the same extent as termination, which lends support to the hypothesis that termination and initiation are coupled. Although termination was almost completely inhibited at 43°C, the majority of the recently synthesized rRNAs were processed to have the correct 3' end of 28S. This finding suggests that 3'-end formation can involve an endonucleolytic cut and is not solely dependent on exonucleolytic trimming of correctly terminated rRNAs.

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Novel expression of the ribosomal RNA genes in the extreme thermophile and archaebacterium Desulfurococcus mobilis

Kjems

Garrett

1987

The EMBO Journal

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The single 16S/23S rRNA operon of the sulfur‐dependent extreme thermophile Desulfurococcus mobilis is transcriptionally uncoupled from the single 5S RNA gene. Transcription of the former operon initiates at five sites, P5–P1. RNA polymerases intiating at sites P5–P2 terminate and then reinitiate at the next downstream site, thus providing a queue of polymerases at the primary initiation site P1. Putative promoter sequences that are AT‐rich lie upstream from each site. Termination occurs at two main sites within long pyrimidine sequences downstream from the 23S RNA gene. A processing site for both large RNAs occurs at a secondary structural feature common to other archaebacterial rRNAs. Transcription of 5S RNA starts mainly at P1/5S at the 5′ end of the gene with a low level of initiation from two upstream sites; a similar mechanism of initiation–termination–reinitiation appears to operate and the sites are all preceded by AT‐rich promoter‐like sequences. Termination occurs a few nucleotides beyound the 3′ end of the 5S RNA. The mature RNA contains ˜133 nucleotides, has a 78% GC bp content and exhibits an unusually extended version of helix I with heterogeneous ends. The expression of the rRNA genes shows characteristics of eukaryotes, eubacteria and archaebacteria.

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Pol I transcription: Which comes first, the end or the beginning?

Cited by 56 publications

References 0 publications

Expression of rRNA Genes and Nucleolus Formation at Ectopic Chromosomal Sites in the Yeast Saccharomyces cerevisiae

Expression of rRNA Genes and Nucleolus Formation at Ectopic Chromosomal Sites in the Yeast Saccharomyces cerevisiae

Analysis of pre-rRNAs in heat-shocked HeLa cells allows identification of the upstream termination site of human polymerase I transcription.

Novel expression of the ribosomal RNA genes in the extreme thermophile and archaebacterium Desulfurococcus mobilis

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