Rapid initial cleavage of nascent pre-rRNA transcripts in yeast

Veinot-Drebot, L M; Singer, Richard A.; Johnston, Gerald C.

doi:10.1016/0022-2836(88)90382-8

Cited by 28 publications

(16 citation statements)

References 38 publications

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“…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%

“…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). Although these studies have elegantly shown an association of pre-rRNA processing factors with pre-rRNA elongation, the temporal coordination of the two processes were yet to be elucidated.…”

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: 81%

Section: Discussionmentioning

confidence: 99%

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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“…The EM results showing unprocessed 5Ј ends in mot1 cells are consistent with results in Fig. 1 showing higher amounts of the 5Ј external transcribed spacer, which is typically very short lived and processed cotranscriptionally (60). The EM results are also consistent with the RNA labeling experiment (Fig.…”

Section: Discussionsupporting

confidence: 81%

Regulation of rRNA Synthesis by TATA-Binding Protein-Associated Factor Mot1

Dasgupta¹,

Sprouse²,

French

et al. 2007

Molecular and Cellular Biology

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“…1). During or immediately after transcription of the rDNA genes, the pre-rRNA is modified, mainly by methylation (32,34). Meanwhile, a large number of ribosomal proteins and nonribosomal components (including proteins and RNA) associate with the pre-rRNA to form a 90S preribosomal particle.…”

mentioning

confidence: 99%

NSR1 is required for pre-rRNA processing and for the proper maintenance of steady-state levels of ribosomal subunits.

Lee¹,

Zabetakis²,

Melese³

1992

Mol. Cell. Biol.

118

104

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NSR1 is a yeast nuclear localization sequence-binding protein showing striking similarity in its domain structure to nucleolin. Cells lacking NSR1 are viable but have a severe growth defect. We show here that NSR1, like nucleolin, is involved in ribosome biogenesis. The nsrl mutant is deficient in pre-rRNA processing such that the initial 35S pre-rRNA processing is blocked and 20S pre-rRNA is nearly absent. The reduced amount of 20S pre-rRNA leads to a shortage of 18S rRNA and is reflected in a change in the distribution of 60S and 40S ribosomal subunits; there is no free pool of 40S subunits, and the free pool of 60S subunits is greatly increased in size. The lack of free 40S subunits or the improper assembly of these subunits causes the nsrl mutant to show sensitivity to the antibiotic paromomycin, which affects protein translation, at concentrations that do not affect the growth of the wild-type strain. Our data support the idea that NSR1 is involved in the proper assembly of pre-rRNA particles, possibly by bringing rRNA and ribosomal proteins together by virtue of its nuclear localization sequence-binding domain and multiple RNA recognition motifs. Alternatively, NSR1 may also act to regulate the nuclear entry of ribosomal proteins required for proper assembly of pre-rRNA particles.In eukaryotic cells, the nucleolus is a specialized subcompartment in which ribosome biogenesis occurs. Pre-rRNA first is transcribed from rDNA genes located in the nucleolus and then undergoes a series of modifications. Ribosomal proteins are imported from the cytoplasm and packed onto the RNA molecule. At the same time, the primary transcript goes through sequential cleavages to generate mature forms of rRNA. Finally, the newly formed ribosomal particles are exported to the cytoplasm.In the yeast Saccharomyces cerevisiae, the largest detectable transcript from the rDNA genes is a 35S pre-rRNA (17), which is rapidly processed into three molecules: the 18S rRNA assembled into 40S ribosomal subunits and the 5.8S and 25S rRNAs found in 60S subunits (Fig. 1). During or immediately after transcription of the rDNA genes, the pre-rRNA is modified, mainly by methylation (32, 34). Meanwhile, a large number of ribosomal proteins and nonribosomal components (including proteins and RNA) associate with the pre-rRNA to form a 90S preribosomal particle. This particle is then split into 66S and 43S preribosomal particles, which are the precursors of the 60S and 40S subunits, respectively (31). While the 66S particles mature completely within the nucleus, the final maturation steps of the 43S particles, including the processing of 20S to 18S rRNA, are completed in the cytoplasm (31,33).Only a few mutations that block specific steps in the pre-rRNA processing pathway have been found. One example is a temperature-sensitive mutation in a gene designated RRPJ that was shown to prevent the 27S-to-25S rRNA cleavage step specifically (1). In another mutant, CLP-8, the efficiency of the processing of 20S to 18S rRNA is greatly reduced, apparently because...

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Rapid initial cleavage of nascent pre-rRNA transcripts in yeast

Cited by 28 publications

References 38 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

Regulation of rRNA Synthesis by TATA-Binding Protein-Associated Factor Mot1

NSR1 is required for pre-rRNA processing and for the proper maintenance of steady-state levels of ribosomal subunits.

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