scholarly journals Condensed mitotic chromatin is accessible to transcription factors and chromatin structural proteins

2004 ◽  
Vol 168 (1) ◽  
pp. 41-54 ◽  
Author(s):  
Danyang Chen ◽  
Miroslav Dundr ◽  
Chen Wang ◽  
Anthony Leung ◽  
Angus Lamond ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Transcriptional Repression ◽  
Core Histone ◽  
Mitotic Chromosomes ◽  
Chromatin Structural ◽  
Polymerase I ◽  
Kinetics Of ◽  
Mitotic Chromatin

During mitosis, chromosomes are highly condensed and transcription is silenced globally. One explanation for transcriptional repression is the reduced accessibility of transcription factors. To directly test this hypothesis and to investigate the dynamics of mitotic chromatin, we evaluate the exchange kinetics of several RNA polymerase I transcription factors and nucleosome components on mitotic chromatin in living cells. We demonstrate that these factors rapidly exchange on and off ribosomal DNA clusters and that the kinetics of exchange varies at different phases of mitosis. In addition, the nucleosome component H1c-GFP also shows phase-specific exchange rates with mitotic chromatin. Furthermore, core histone components exchange at detectable levels that are elevated during anaphase and telophase, temporally correlating with H3-K9 acetylation and recruitment of RNA polymerase II before the onset of bulk RNA synthesis at mitotic exit. Our findings indicate that mitotic chromosomes in general and ribosomal genes in particular, although highly condensed, are accessible to transcription factors and chromatin proteins. The phase-specific exchanges of nucleosome components during late mitotic phases are consistent with an emerging model of replication independent core histone replacement.

Control points in eucaryotic ribosome biogenesis

1991 ◽  
Vol 69 (1) ◽  
pp. 5-22 ◽  
Author(s):  
D. E. Larson ◽  
P. Zahradka ◽  
B. H. Sells
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Rna Polymerase Iii ◽  
Ribosomal Subunits ◽  
Rrna Species ◽  
Polymerase I ◽  
Ribosomal Precursor ◽  
Precursor Molecules

Ribosome biogenesis in eucaryotic cells involves the coordinated synthesis of four rRNA species, transcribed by RNA polymerase I (18S, 28S, 5.8S) and RNA polymerase III (5S), and approximately 80 ribosomal proteins translated from mRNAs synthesized by RNA polymerase II. Assembly of the ribosomal subunits in the nucleolus, the site of 45S rRNA precursor gene transcription, requires the movement of 5S rRNA and ribosomal proteins from the nucleoplasm and cytoplasm, respectively, to this structure. To integrate these events and ensure the balanced production of individual ribosomal components, different strategies have been developed by eucaryotic organisms in response to a variety of physiological changes. This review presents an overview of the mechanisms modulating the production of ribosomal precursor molecules and the rate of ribosome biogenesis in various biological systems.Key words: rRNA, ribosomal proteins, nucleolus, ribosome.

Evidence that the SKI antiviral system of Saccharomyces cerevisiae acts by blocking expression of viral mRNA

1993 ◽  
Vol 13 (7) ◽  
pp. 4331-4341
Author(s):  
W R Widner ◽  
R B Wickner
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Copy Number ◽  
Dsrna Virus ◽  
Cdna Clones ◽  
Viral Mrnas ◽  
Nucleolar Proteins ◽  
Toxin Secretion ◽  
Polymerase I ◽  
Beta Galactosidase

The SKI2 gene is part of a host system that represses the copy number of the L-A double-stranded RNA (dsRNA) virus and its satellites M and X dsRNA, of the L-BC dsRNA virus, and of the single-stranded replicon 20S RNA. We show that SKI2 encodes a 145-kDa protein with motifs characteristic of helicases and nucleolar proteins and is essential only in cells carrying M dsRNA. Unexpectedly, Ski2p does not repress M1 dsRNA copy number when M1 is supported by aN L-A cDNA clone; nonetheless, it did lower the levels of M1 dsRNA-encoded toxin produced. Since toxin secretion from cDNA clones of M1 is unaffected by Ski2p, these data suggest that Ski2p acts by specifically blocking translation of viral mRNAs, perhaps recognizing the absence of cap or poly(A). In support of this idea, we find that Ski2p represses production of beta-galactosidase from RNA polymerase I [no cap and no poly(A)] transcripts but not from RNA polymerase II (capped) transcripts.

scholarly journals Nuclear distribution of transcription factors in relation to sites of transcription and RNA polymerase II

1997 ◽  
Vol 110 (15) ◽  
pp. 1781-1791 ◽  
Author(s):  
M.A. Grande ◽  
I. van der Kraan ◽  
L. de Jong ◽  
R. van Driel
Keyword(s):  
Transcription Factors ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Transcription Initiation ◽  
Glucocorticoid Receptors ◽  
Cultured Cells ◽  
Spatial Relationship ◽  
Immunofluorescence Labelling ◽  
Transcription Sites ◽  
Nuclear Domains

We have investigated the spatial relationship between sites containing newly synthesized RNA and domains containing proteins involved in transcription, such as RNA polymerase II and the transcription factors TFIIH, Oct1, BRG1, E2F-1 and glucocorticoid receptors, using dual immunofluorescence labelling followed by confocal microscopy on cultured cells. As expected, a high degree of colocalisation between the RNA polymerase II and sites containing newly synthesised RNA was observed. Like the newly synthesised RNA and the RNA polymerase II, we found that all the transcription factors that we studied are distributed more or less homogeneously throughout the nucleoplasm, occupying numerous small domains. In addition to these small domains, TFIIH was found concentrated in coiled bodies and Oct1 in a single large domain of about 1.5 microm in 30% of the cells in an asynchronous HeLa cell culture. Remarkably, we found little or no relationship between the spatial distribution of the glucocorticoid receptor, Oct1 and E2F-1 on the one hand and RNA polymerase II and transcription sites on the other hand. In contrast, a significant but incomplete overlap was observed between the spatial distributions of transcription sites and BRG1 and TFIIH. These results indicate that many of the transcription factor-rich nuclear domains are not actively involved in transcription. They may represent incomplete transcription initiation complexes, inhibitory complexes, or storage sites.

scholarly journals Deciphering Kinetics of RNA Polymerase I Multi-Nucleotide Transcription

2020 ◽  
Vol 118 (3) ◽  
pp. 543a
Author(s):  
Zachariah Ingram ◽  
David A. Schneider ◽  
Aaron L. Lucius
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase I ◽  
Polymerase I ◽  
Kinetics Of
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