scholarly journals A polymerase switch in the synthesis of rRNA in Saccharomyces cerevisiae.

1995 ◽  
Vol 15 (5) ◽  
pp. 2420-2428 ◽  
Author(s):  
H Conrad-Webb ◽  
R A Butow
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Ribosomal Dna ◽  
Sole Source ◽  
Rna Polymerase I ◽  
Yeast Cells ◽  
Dna Repeat ◽  
Polymerase I ◽  
Respiratory Deficient

Transcription of ribosomal DNA by RNA polymerase I is believed to be the sole source of the 25S, 18S, and 5.8S rRNAs in wild-type cells of Saccharomyces cerevisiae. Here we present evidence for a switch from RNA polymerase I to RNA polymerase II in the synthesis of a substantial fraction of those rRNAs in respiratory-deficient (petite) cells. The templates for the RNA polymerase II transcripts are largely, if not exclusively, episomal copies of ribosomal DNA arising from homologous recombination events within the ribosomal DNA repeat on chromosome XII. Ribosomal DNA contains a cryptic RNA polymerase II promoter that is activated in petites; it overlaps the RNA polymerase I promoter and produces a transcript equivalent to the 35S precursor rRNA made by RNA polymerase I. Yeast cells that lack RNA polymerase I activity, because of a disruption of the RPA135 gene that encodes subunit II of the enzyme, can survive by using the RNA polymerase II promoter in ribosomal DNA to direct the synthesis of the 35S rRNA precursor. This polymerase switch could provide cells with a mechanism to synthesize rRNA independent of the controls of RNA polymerase I transcription.

Human ribosomal DNA fragments amplified in hamster cells are transcribed only by RNA polymerase II and are not silver stained

1987 ◽  
Vol 7 (3) ◽  
pp. 1289-1292
Author(s):  
V N Dhar ◽  
D A Miller ◽  
A B Kulkarni ◽  
O J Miller
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Ribosomal Dna ◽  
Chinese Hamster ◽  
Rna Polymerase I ◽  
Rrna Gene ◽  
Methotrexate Resistance ◽  
Selection For ◽  
Polymerase I ◽  
Chromosome Regions

Cloned human rRNA gene fragments that included the promoter region were introduced into Chinese hamster dihydrofolate reductase-deficient (dhfr-) cells by cotransformation with a dhfr minigene and amplified by selection for methotrexate resistance. The human ribosomal DNA was transcribed by RNA polymerase II, not RNA polymerase I or III. The metaphase chromosome regions containing the transcriptionally active human ribosomal DNA failed to show silver staining.

Transcription by RNA polymerase I stimulates mitotic recombination in Saccharomyces cerevisiae

1989 ◽  
Vol 9 (8) ◽  
pp. 3464-3472
Author(s):  
S E Stewart ◽  
G S Roeder
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Ribosomal Dna ◽  
Initiation Site ◽  
Mitotic Recombination ◽  
Rna Polymerase I ◽  
Dna Array ◽  
Chromosomal Sequences ◽  
Polymerase I ◽  
The Relationship

The recombination-stimulating sequence HOT1 is derived from the ribosomal DNA array of Saccharomyces cerevisiae and corresponds to sequences that promote transcription by RNA polymerase I. When inserted at a chromosomal location outside the ribosomal DNA array, HOT1 stimulates mitotic recombination in the adjacent sequences. To investigate the relationship between transcription and recombination, transcription promoted by HOT1 was directly examined. These studies demonstrated that transcription starts at the RNA polymerase I initiation site in HOT1 and proceeds through the chromosomal sequences in which recombination is enhanced. Linker insertion mutations in HOT1 were generated and assayed for recombination stimulation and for promoter function; this analysis demonstrated that the same sequences are required for both activities. These results indicate that the ability of HOT1 to enhance recombination is related to, and most likely dependent on, its ability to promote transcription.

scholarly journals RNA Polymerase I Transcription Silences Noncoding RNAs at the Ribosomal DNA Locus in Saccharomyces cerevisiae

2009 ◽  
Vol 9 (2) ◽  
pp. 325-335 ◽  
Author(s):  
Elisa Cesarini ◽  
Francesca Romana Mariotti ◽  
Francesco Cioci ◽  
Giorgio Camilloni
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Ribosomal Dna ◽  
Rna Polymerase Iii ◽  
Noncoding Rnas ◽  
Rdna Locus ◽  
Rna Polymerase I ◽  
Pol Ii ◽  
Pol I ◽  
Polymerase I

ABSTRACT In Saccharomyces cerevisiae the repeated units of the ribosomal locus, transcribed by RNA polymerase I (Pol I), are interrupted by nontranscribed spacers (NTSs). These NTS regions are transcribed by RNA polymerase III to synthesize 5S RNA and by RNA polymerase II (Pol II) to synthesize, at low levels, noncoding RNAs (ncRNAs). While transcription of both RNA polymerase I and III is highly characterized, at the ribosomal DNA (rDNA) locus only a few studies have been performed on Pol II, whose repression correlates with the SIR2-dependent silencing. The involvement of both chromatin organization and Pol I transcription has been proposed, and peculiar chromatin structures might justify “ribosomal” Pol II silencing. Reporter genes inserted within the rDNA units have been employed for these studies. We studied, in the natural context, yeast mutants differing in Pol I transcription in order to find whether correlations exist between Pol I transcription and Pol II ncRNA production. Here, we demonstrate that silencing at the rDNA locus represses ncRNAs with a strength inversely proportional to Pol I transcription. Moreover, localized regions of histone hyperacetylation appear in cryptic promoter elements when Pol II is active and in the coding region when Pol I is functional; in addition, DNA topoisomerase I site-specific activity follows RNA polymerase I transcription. The repression of ncRNAs at the rDNA locus, in response to RNA polymerase I transcription, could represent a physiological circuit control whose mechanism involves modification of histone acetylation.

scholarly journals A Sequence-Specific Interaction between the Saccharomyces cerevisiae rRNA Gene Repeats and a Locus Encoding an RNA Polymerase I Subunit Affects Ribosomal DNA Stability

2014 ◽  
Vol 35 (3) ◽  
pp. 544-554 ◽  
Author(s):  
Inswasti Cahyani ◽  
Andrew G. Cridge ◽  
David R. Engelke ◽  
Austen R. D. Ganley ◽  
Justin M. O'Sullivan
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Ribosomal Dna ◽  
Intergenic Region ◽  
Copy Number ◽  
Rna Polymerase I ◽  
Intergenic Sequence ◽  
Polymerase I ◽  
Rdna Copy ◽  
Rdna Copy Number

The spatial organization of eukaryotic genomes is linked to their functions. However, how individual features of the global spatial structure contribute to nuclear function remains largely unknown. We previously identified a high-frequency interchromosomal interaction within theSaccharomyces cerevisiaegenome that occurs between the intergenic spacer of the ribosomal DNA (rDNA) repeats and the intergenic sequence between the locus encoding the second largest RNA polymerase I subunit and a lysine tRNA gene [i.e.,RPA135-tK(CUU)P]. Here, we used quantitative chromosome conformation capture in combination with replacement mapping to identify a 75-bp sequence within theRPA135-tK(CUU)Pintergenic region that is involved in the interaction. We demonstrate that theRPA135-IGS1 interaction is dependent on the rDNA copy number and the Msn2 protein. Surprisingly, we found that the interaction does not governRPA135transcription. Instead, replacement of a 605-bp region within theRPA135-tK(CUU)Pintergenic region results in a reduction in theRPA135-IGS1 interaction level and fluctuations in rDNA copy number. We conclude that the chromosomal interaction that occurs between theRPA135-tK(CUU)Pand rDNA IGS1 loci stabilizes rDNA repeat number and contributes to the maintenance of nucleolar stability. Our results provide evidence that the DNA loci involved in chromosomal interactions are composite elements, sections of which function in stabilizing the interaction or mediating a functional outcome.

scholarly journals Human ribosomal DNA fragments amplified in hamster cells are transcribed only by RNA polymerase II and are not silver stained.

1987 ◽  
Vol 7 (3) ◽  
pp. 1289-1292 ◽  
Author(s):  
V N Dhar ◽  
D A Miller ◽  
A B Kulkarni ◽  
O J Miller
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Ribosomal Dna ◽  
Chinese Hamster ◽  
Rna Polymerase I ◽  
Rrna Gene ◽  
Methotrexate Resistance ◽  
Selection For ◽  
Polymerase I ◽  
Chromosome Regions

Cloned human rRNA gene fragments that included the promoter region were introduced into Chinese hamster dihydrofolate reductase-deficient (dhfr-) cells by cotransformation with a dhfr minigene and amplified by selection for methotrexate resistance. The human ribosomal DNA was transcribed by RNA polymerase II, not RNA polymerase I or III. The metaphase chromosome regions containing the transcriptionally active human ribosomal DNA failed to show silver staining.

Structural alterations of the nucleolus in mutants of Saccharomyces cerevisiae defective in RNA polymerase I

1993 ◽  
Vol 13 (4) ◽  
pp. 2441-2455
Author(s):  
M Oakes ◽  
Y Nogi ◽  
M W Clark ◽  
M Nomura
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Rna Polymerase I ◽  
Rrna Synthesis ◽  
Rrna Processing ◽  
Structural Element ◽  
Nucleolar Structure ◽  
Pol I ◽  
Polymerase I

We have previously constructed mutants of Saccharomyces cerevisiae in which the gene for the second-largest subunit of RNA polymerase I (Pol I) is deleted. In these mutants, rRNA is synthesized by RNA polymerase II from a hybrid gene consisting of the 35S rRNA coding region fused to the GAL7 promoter on a plasmid. These strains thus grow in galactose but not glucose media. By immunofluorescence microscopy using antibodies against the known nucleolar proteins SSB1 and fibrillarin, we found that the intact crescent-shaped nucleolar structure is absent in these mutants; instead, several granules (called mininucleolar bodies [MNBs]) that stained with these antibodies were seen in the nucleus. Conversion of the intact nucleolar structure to MNBs was also observed in Pol I temperature-sensitive mutants at nonpermissive temperatures. These MNBs may structurally resemble prenucleolar bodies observed in higher eukaryotic cells and may represent a constituent of the normal nucleolus. Furthermore, cells under certain conditions that inhibit rRNA synthesis did not cause conversion of the nucleolus to MNBs. Thus, the role of Pol I in the maintenance of the intact nucleolar structure might include a role as a structural element in addition to (or instead of) a functional role to produce rRNA transcripts. Our study also shows that the intact nucleolar structure is not absolutely required for rRNA processing, ribosome assembly, or cell growth and that MNBs are possibly functional in rRNA processing in the Pol I deletion mutants.

scholarly journals Structural alterations of the nucleolus in mutants of Saccharomyces cerevisiae defective in RNA polymerase I.

1993 ◽  
Vol 13 (4) ◽  
pp. 2441-2455 ◽  
Author(s):  
M Oakes ◽  
Y Nogi ◽  
M W Clark ◽  
M Nomura
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Rna Polymerase I ◽  
Rrna Synthesis ◽  
Rrna Processing ◽  
Structural Element ◽  
Nucleolar Structure ◽  
Pol I ◽  
Polymerase I

We have previously constructed mutants of Saccharomyces cerevisiae in which the gene for the second-largest subunit of RNA polymerase I (Pol I) is deleted. In these mutants, rRNA is synthesized by RNA polymerase II from a hybrid gene consisting of the 35S rRNA coding region fused to the GAL7 promoter on a plasmid. These strains thus grow in galactose but not glucose media. By immunofluorescence microscopy using antibodies against the known nucleolar proteins SSB1 and fibrillarin, we found that the intact crescent-shaped nucleolar structure is absent in these mutants; instead, several granules (called mininucleolar bodies [MNBs]) that stained with these antibodies were seen in the nucleus. Conversion of the intact nucleolar structure to MNBs was also observed in Pol I temperature-sensitive mutants at nonpermissive temperatures. These MNBs may structurally resemble prenucleolar bodies observed in higher eukaryotic cells and may represent a constituent of the normal nucleolus. Furthermore, cells under certain conditions that inhibit rRNA synthesis did not cause conversion of the nucleolus to MNBs. Thus, the role of Pol I in the maintenance of the intact nucleolar structure might include a role as a structural element in addition to (or instead of) a functional role to produce rRNA transcripts. Our study also shows that the intact nucleolar structure is not absolutely required for rRNA processing, ribosome assembly, or cell growth and that MNBs are possibly functional in rRNA processing in the Pol I deletion mutants.

scholarly journals Transcription by RNA polymerase I stimulates mitotic recombination in Saccharomyces cerevisiae.

1989 ◽  
Vol 9 (8) ◽  
pp. 3464-3472 ◽  
Author(s):  
S E Stewart ◽  
G S Roeder
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Ribosomal Dna ◽  
Initiation Site ◽  
Mitotic Recombination ◽  
Rna Polymerase I ◽  
Dna Array ◽  
Chromosomal Sequences ◽  
Polymerase I ◽  
The Relationship

The recombination-stimulating sequence HOT1 is derived from the ribosomal DNA array of Saccharomyces cerevisiae and corresponds to sequences that promote transcription by RNA polymerase I. When inserted at a chromosomal location outside the ribosomal DNA array, HOT1 stimulates mitotic recombination in the adjacent sequences. To investigate the relationship between transcription and recombination, transcription promoted by HOT1 was directly examined. These studies demonstrated that transcription starts at the RNA polymerase I initiation site in HOT1 and proceeds through the chromosomal sequences in which recombination is enhanced. Linker insertion mutations in HOT1 were generated and assayed for recombination stimulation and for promoter function; this analysis demonstrated that the same sequences are required for both activities. These results indicate that the ability of HOT1 to enhance recombination is related to, and most likely dependent on, its ability to promote transcription.

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