Association of Yeast RNA Polymerase I with a Nucleolar Substructure Active in Rrna Synthesis and Processing

Fath, Stephan; Milkereit, Philipp; Podtelejnikov, Alexandre V.; Bischler, Nicolas; Schultz, Patrick; Bier, Mirko; Mann, Matthias; Tschochner, Herbert

doi:10.1083/jcb.149.3.575

Cited by 54 publications

(54 citation statements)

References 79 publications

(146 reference statements)

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“…Together, our results suggest that the interaction between UBF and fibrillarin is most likely dependent on the ability of fibrillarin to be assembled into snoRNPs, one of which is U3 snoRNP, thereby supporting the idea that UBF interacts with snoRNP complexes rather than with free fibrillarin. These data are consistent with reports that pol I and prerRNA processing factors (U3 snoRNP) are in the same complex in yeast (Fath et al, 2000). …”

supporting

confidence: 83%

“…These observations indicate that transcription factors can be mobilized to the site of transcription separately from pre-rRNA processing factors, which are recruited only in the presence of the specific substrate. This suggests that the association of pre-rRNA processing factors to the newly transcribed rRNA is sequential and is on anneeded basis.Our findings that pol I transcription factors interact with pre-rRNA processing factors are consistent with recent studies in nonmammalian systems that found transcription factors in the same complex with pre-rRNA processing factors (Fath et al, 2000;Gallagher et al, 2004) and coordination between the two processes (Veinot-Drebot et al, 1988;Caparros-Ruiz et al, 1997;Dragon et al, 2002;Gallagher et al, 2004;Osheim et al, 2004;Saez-Vasquez et al, 2004). Studies in yeast showed that most nascent pre-rRNA transcripts no longer contain 5Ј external transcribed spacer sequences (Veinot-Drebot et al, 1988) and that the initial steps of pre-rRNA processing take place before the completion of pre-rRNA transcription (Dragon et al, 2002;Osheim et al, 2004).…”

supporting

confidence: 81%

“…The coordination between transcription and pre-rRNA processing could be facilitated through at least two different mechanisms. The transcription and processing factors could be corecruited to the site of transcription in a large complex, as the pol II system is coordinated, which is an idea that is supported by a number of published studies (Fath et al, 2000;Saez-Vasquez et al, 2004). Alternatively, processing factors could be recruited to the sites of transcription only when the nascent pre-rRNA substrate becomes available.…”

mentioning

confidence: 67%

“…Studies in plants show that a complex containing a snoRNP that includes fibrillarin and nucleolin-like proteins is competent for both rDNA binding (in the absence of transcription) and pre-rRNA processing in vitro, suggesting that they are in the same complex before rDNA binding (Caparros-Ruiz et al, 1997;Saez-Vasquez et al, 2004). Additionally, a nucleolar RNP complex containing pol I transcription and pre-rRNA processing factors has been isolated in yeast cells that were pol I deficient or transcriptionally incompetent (Fath et al, 2000). These studies suggest the existence of a preassembled complex with transcription and processing factors that binds rDNA independently of transcription.…”

Section: Discussionmentioning

confidence: 99%

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Pol I Transcription and Pre-rRNA Processing Are Coordinated in a Transcription-dependent Manner in Mammalian Cells

Kopp

Gasiorowski

Chen

et al. 2007

MBoC

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Pre-rRNA synthesis and processing are key steps in ribosome biogenesis. Although recent evidence in yeast suggests that these two processes are coupled, the nature of their association is unclear. In this report, we analyze the coordination between rDNA transcription and pre-rRNA processing in mammalian cells. We found that pol I transcription factor UBF interacts with pre-rRNA processing factors as analyzed by immunoprecipitations, and the association depends on active rRNA synthesis. In addition, injections of plasmids containing the human rDNA promoter and varying lengths of 18S rDNA into HeLa nuclei show that pol I transcription machinery can be recruited to rDNA promoters regardless of the product that is transcribed, whereas subgroups of pre-rRNA processing factors are recruited to plasmids only when specific pre-rRNA fragments are produced. Our observations suggest a model for sequential recruitment of pol I transcription factors and pre-rRNA processing factors to elongating pre-rRNA on an as-needed basis rather than corecruitment to sites of active transcription. INTRODUCTIONNucleoli contain hundreds of tandem rRNA genes and a large number of factors necessary for transcription of ribosomal DNA (rDNA), processing of pre-rRNA, and ribosome assembly. Electron microscopic imaging of nucleoli reveal three distinct subcompartments: the fibrillar centers (FC), dense fibrillar components (DFC), and granular components (GC;Huang, 2002). It is at the FC/DFC border that RNA polymerase I (pol I) and other pol I-specific transcription factors associate to form the pol I preinitiation complex (PIC) at rRNA promoters (Grummt, 2003;Grummt and Pikaard, 2003) for transcription of rDNA (Raska et al., 2004). In vivo activation of the human rRNA promoter requires proteinprotein interactions between the DNA-binding protein, upstream binding factor (UBF1), and SL1 for the targeting of pol I and stable PIC formation (Bell et al., 1988;Friedrich et al., 2005). In combination with several other evolutionarily conserved proteins, these and other pol I transcription factors confer pol I promoter specificity to produce a single polycistronic pre-rRNA transcript (45S pre-rRNA in humans; Grummt, 2003;Grummt and Pikaard, 2003).A large number of small nucleolar ribonucleoproteins (snoRNPs), composed of small nucleolar RNAs (snoRNAs) and their associated proteins, as well as more than 100 protein cofactors, are responsible for processing the 45S transcript (Fromont-Racine et al., 2003;Granneman and Baserga, 2005). The box C/D snoRNA U3 and its associated proteins are required for the initial cleavages of the 5Ј end of pre-rRNA at sites A 0 , A 1 , and A 2 and are thereby involved in the release of the 18S precursor (Fromont-Racine et al., 2003;Granneman and Baserga, 2005). Yeast U3 snoRNA exists in at least two types of complexes in vitro: a 12S monoparticle (Billy et al., 2000;Granneman et al., 2003) and a larger ϳ90S complex termed the small subunit (SSU) processome (Fabrizio et al., 1994;Dragon et al., 2002). The 12S monoparticle pre...

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supporting

confidence: 83%

supporting

confidence: 81%

mentioning

confidence: 67%

Section: Discussionmentioning

confidence: 99%

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Pol I Transcription and Pre-rRNA Processing Are Coordinated in a Transcription-dependent Manner in Mammalian Cells

Kopp

Gasiorowski

Chen

et al. 2007

MBoC

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“…To find out whether Noc4p is involved in ribosome biogenesis, we sought to characterize Noc4p, which is an essential protein of 63 kDa. Together with the other Noc proteins, Noc4p is enriched in the previously isolated large nucleolar subcomplex (data not shown) that contains many factors involved in rDNA transcription and ribosome biogenesis (16). Consistent with this biochemical data, chromosomally encoded Noc4p-GFP is located in the nucleolus (Fig.…”

Section: Noc4psupporting

confidence: 72%

A Noc Complex Specifically Involved in the Formation and Nuclear Export of Ribosomal 40 S Subunits

Milkereit

Strauß

Baßler

et al. 2003

Journal of Biological Chemistry

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116

130

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Formation and nuclear export of 60 S pre-ribosomes requires many factors including the heterodimeric Noc1-Noc2 and Noc2-Noc3 complexes. Here, we report another Noc complex with a specific role in 40 S subunit biogenesis. This complex consists of Noc4p, which exhibits the conserved Noc domain and is homologous to Noc1p, and Nop14p, a nucleolar protein with a role in 40 S subunit formation. Moreover, noc4 thermosensitive mutants are defective in 40 S biogenesis, and rRNA processing is inhibited at early cleavage sites A 0 , A 1 , and A 2 . Using a fluorescence-based visual assay for 40 S subunit export, we observe a strong nucleolar accumulation of the Rps2p-green fluorescent protein reporter in noc4 ts mutants, but 60 S subunit export was normal. Thus, Noc4p and Nop14p form a novel Noc complex with a specific role in nucleolar 40 S subunit formation and subsequent export to the cytoplasm.Eukaryotic ribosome biogenesis is spatially organized into different subcellular compartments. Most steps in the pathway leading to mature ribosomes occur in the nucleolus, a specialized nuclear substructure, which includes transcription of the rDNA by RNA polymerase I, modification of the synthesized precursor RNA, and the assembly of both many ribosomal and non-ribosomal proteins with pre-ribosomal RNA (1). In the yeast Saccharomyces cerevisiae the resulting large ribonucleoprotein complex forms the 90 S pre-ribosome, which is split into precursor particles for the mature 40 S and 60 S ribosomal subunit (2). During or after their maturation the pre-ribosomes leave the nucleolus, move toward the nuclear pore, gain export competence, and are finally exported into the cytoplasm. Some maturation steps like processing of the 20 S rRNA intermediate within the 40 S subunit and the association of a few ribosomal proteins to the ribosomes occur rather late, even in the cytoplasm (3).Many factors known to be involved in biosynthesis and maturation of ribosomes were identified and characterized in S. cerevisiae (4,5). This organism represents a well suited model organism to study eukaryotic ribosome biogenesis, because homologues of the factors required are found in many eukaryotes. Of the more than 70 non-ribosomal proteins that participate in generation of ribosomes, most have been described to be required for modification of rRNA or removal of the external and internal spacer sequences from the precursor 35 S pre-RNA. End products of the rRNA processing pathways are the 18 S rRNA, which is present in the 40 S subunit and the 25 S and 5.8 S rRNA, as well as the RNA polymerase III-encoded 5 S rRNA, which are the rRNA constituents of the 60 S subunit. Among the transacting factors involved to produce mature 40 S and 60 S subunits are nucleases, putative RNA helicases, RNA modifying proteins, and proteins associated with small nucleolar RNAs (4, 5) (see also www.expasy.ch/linder/proteins.html).Folding, processing, and maturation of the rRNA is coordinated with the association of ribosomal proteins, with the assembly and disassembly of tran...

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Current Awareness

2000

Yeast

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In order to keep subscribers up‐to‐date with the latest developments in their field, this current awareness service is provided by John Wiley & Sons and contains newly‐published material on yeasts. Each bibliography is divided into 10 sections. 1 Books, Reviews & Symposia; 2 General; 3 Biochemistry; 4 Biotechnology; 5 Cell Biology; 6 Gene Expression; 7 Genetics; 8 Physiology; 9 Medical Mycology; 10 Recombinant DNA Technology. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. (3 weeks journals ‐ search completed 21st June 2000)

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Association of Yeast RNA Polymerase I with a Nucleolar Substructure Active in Rrna Synthesis and Processing

Cited by 54 publications

References 79 publications

Pol I Transcription and Pre-rRNA Processing Are Coordinated in a Transcription-dependent Manner in Mammalian Cells

Pol I Transcription and Pre-rRNA Processing Are Coordinated in a Transcription-dependent Manner in Mammalian Cells

A Noc Complex Specifically Involved in the Formation and Nuclear Export of Ribosomal 40 S Subunits

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