Efficient synthesis, termination and release of RNA polymerase III transcripts in Xenopusextracts depleted of La protein

Lin-Marq, Nathalie; Clarkson, Stuart G.

doi:10.1093/emboj/17.7.2033

Cited by 43 publications

(30 citation statements)

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“…Although recombinant human La was found to influence pol III transcription under certain conditions in vitro, other work in several systems found no effect of La on transcription (23,24). Nevertheless, our results show that La can be found at all three types of pol III template in living cells.…”

Section: Discussioncontrasting

confidence: 61%

“…Saccharomyces cerevisiae strains, which are null for the La homologue, are viable and have no reduction of pol III transcription (21,22). Immunodepletion of La from Xenopus or HeLa extracts did not result in any discernible decrease in pol III transcription (23,24). Furthermore, a highly purified human system that is fully active for U6 gene transcription did not contain any detectable La (9).…”

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confidence: 96%

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Human La is found at RNA polymerase III-transcribed genes in vivo

Fairley

Kantidakis

Kenneth

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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The human La autoantigen can bind to nascent RNA transcripts and has also been postulated to act as an RNA polymerase III (pol III) transcription initiation and termination factor. Here, we show by chromatin immunoprecipitation (ChIP) that La is associated with pol III-transcribed genes in vivo. In contrast, the Ro autoantigen, which can also bind pol III transcripts, is not found at these genes. The putative pol III transcription factors NF1 and TFIIA are also not detected at class III genes. Binding of La remains when transcription is repressed at mitosis and does not correlate with the presence of polymerase at the gene. However, gene occupancy depends on the phosphorylation status of La, with the less prevalent, unphosphorylated form being found selectively on pol III templates.La ͉ NF1 ͉ TFIIA ͉ chromatin immunoprecipitation ͉ RNA polymerase III transcription R NA polymerase III (pol III) is responsible for the production of a number of short, untranslated RNAs that are essential for cellular growth; pol III transcription is therefore a major determinant of the biosynthetic capacity of cells (reviewed in refs. 1 and 2). The key to understanding how this influence is regulated is the identification of factors that can control expression. Pol III promoters can be divided into three types that utilize different transcription factors for their activity. Type 1 and 2 promoters, exemplified by the 5S rRNA and tRNA promoters, respectively, recruit TFIIIA and͞or TFIIIC, through binding to sequence-specific elements within the gene (reviewed in refs. 3 and 4). TFIIIC in turn recruits a TFIIIB complex containing Brf1, TBP, and Bdp1, which is able to recruit the polymerase through protein-protein interactions. In contrast, type 3 promoters, such as that for U6 small nuclear RNA (snRNA), contain gene external elements that are recognized by the SNAPc complex and TFIIIB (4); however, the TFIIIB in this case differs from that used for type 1 and type 2 promoters in utilizing Brf2 instead of Brf1 (4, 5). In addition to these basal transcription factors, a number of other proteins have been found to influence pol III transcription in mammals. Some of these regulators have been shown to associate with pol III templates in vivo, including c-Myc (6), RB (7), ␤-actin (8), and the protein kinase CK2 (9, 10). However, there are a number of other proteins, including La, TFIIA and NF1, for which a role in pol III transcription has been suggested from experiments in vitro, but which has not been confirmed in vivo.The human autoantigen La is a highly abundant protein found associated with newly synthesized pol III products (11,12). La binds to nascent pol III transcripts through the UUU-OH at their 3Ј ends, which corresponds to the pol III termination signal, and also has affinity for their 5Ј ends (13-15). One of the functions of La is in the stabilization of these transcripts, which promotes their processing to the mature forms (16). However, La has also been reported to have effects on pol III transcription. Immunodepletion of La...

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Section: Discussioncontrasting

confidence: 61%

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confidence: 96%

Human La is found at RNA polymerase III-transcribed genes in vivo

Fairley

Kantidakis

Kenneth

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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“…The La protein binds to the 3Ј terminus of the newly synthesized transcript and protects this end from digestion by exonucleases Fan et al 1998;Lin-Marq and Clarkson 1998). The La protein-bound pre-tRNA is the substrate for the ribonucleoprotein enzyme RNase P, which removes the 5Ј leader sequence by a single endonucleolytic cleavage (for review, see Frank and Pace 1998).…”

Section: Binding By the La Protein Is Required For The Normal Pathwaymentioning

confidence: 99%

The trials and travels of tRNA: Figure 1.

Wolin¹,

Matera²

1999

Genes Dev.

138

114

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For relatively small molecules, the biogenesis of functional mature tRNAs is an amazingly complicated process. All tRNAs are transcribed initially as precursors containing 5Ј leader and 3Ј trailer sequences that must be removed by processing. Pre-tRNAs also undergo a complex set of base modifications that are carried out by a series of enzymes that recognize specific features of tRNA structure. In addition, eukaryotic tRNAs have CCA added to their 3Ј ends by a specialized nucleotidyltransferase. A subset of eukaryotic pre-tRNAs also contain intervening sequences, which are removed by a dedicated set of tRNA splicing enzymes. Lastly, tRNAs must be exported from the nucleus to the cytoplasm, and must undergo aminoacylation to participate in protein synthesis. Although the basic features of the tRNA biogenesis pathway have been appreciated for at least a decade, work in a number of laboratories over the last several years has resulted in several novel and unexpected insights into this complex process. For example, it was revealed recently that tRNAs are recognized and exported to the cytoplasm by a specialized export receptor, and that recognition by this export receptor is part of a quality control mechanism that ensures that incompletely processed and mutant RNAs will be retained in the nucleus. Furthermore, recent evidence suggests that certain of the various tRNA processing steps take place in discrete subcellular compartments, such that at least some steps of the tRNA biogenesis pathway are spatially as well as temporally ordered.The eukaryotic tRNA biogenesis pathway is best understood in the budding yeast Saccharomyces cerevisiae, primarily due to the ease of combining genetics with biochemistry in this organism. However, virtually all components that have been identified in yeast have counterparts in higher cells, as would be expected for such a highly conserved process. Therefore, in this review, we emphasize recent results from yeast but also draw upon data from both prokaryotes and higher eukaryotic species. We provide an update on what is presently known about the processing events and paths taken by eukaryotic tRNAs following termination of transcription, culminating in their export to the cytoplasm. For more extensive descriptions of the enzymology of end-maturation, nucleotide modification, and tRNA splicing, see the following excellent reviews: Hopper and Martin (1992); Westaway and Abelson (1995); Grosjean et al. (1997);and Abelson et al. (1998). Binding by the La protein is required for the normal pathway of tRNA end maturationIn eukaryotes, the first protein that binds to all newly synthesized pre-tRNAs is the La autoantigen, a highly abundant nuclear phosphoprotein. The La protein binds to the 3Ј terminus of the newly synthesized transcript and protects this end from digestion by exonucleases Fan et al. 1998;Lin-Marq and Clarkson 1998). The La protein-bound pre-tRNA is the substrate for the ribonucleoprotein enzyme RNase P, which removes the 5Ј leader sequence by a single endonucleolytic cleavag...

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“…Binding occurs via the common UUU-OH 3Ј-terminal motif which results from transcription termination within the Pol III termination signal, oligo(dT) (58,89,113,115,136). As a result of UUU-OH binding and other activities, human La (hLa) also appears to function in transcription termination and reinitiation by Pol III (29, 42, 44-47, 87, 88), although this remains controversial (43,82,146,154).La proteins have been differentially expanded in the mass and domain complexity of their C-terminal domains (CTD) and utilize different pathways of nuclear import in different species. La protein of the yeast Saccharomyces cerevisiae is imported into the nucleus via a pathway that is different from the pathway used by the fission yeast, Schizosaccharomyces pombe, and higher eukaryotes (117).…”

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confidence: 99%

mentioning

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Recognition of Nascent RNA by the Human La Antigen: Conserved and Divergent Features of Structure and Function

Maraia

Intine

2001

Molecular and Cellular Biology

106

114

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La is a conserved RNA-binding phosphoprotein that interacts with a large variety of ligands. The most ubiquitous function of La is association with newly synthesized RNA polymerase (Pol) III transcripts via their common UUU-OH 3Ј termini and stabilization of these against exonucleolytic digestion. Accumulating evidence also indicates an activity for La in internal ribosome entry site-mediated translation in mammalian cells and in the metabolism of a subset of 3Ј-processed snRNA intermediates that end in uridylates but are synthesized by Pol II. The most highly conserved region of La resides in the N-terminal domain (NTD), and this appears to mediate highaffinity UUU-OH recognition. As critically reviewed here by comparison to a consensus core RNA recognition motif (RRM) structure, the NTD can be modeled into a pair of tandem RRMs. In addition to the conserved NTD, human La (hLa) protein contains a C-terminal domain (CTD) that harbors a third RRM and a potential Walker A motif that appears to recognize the 5Ј-ppp ends of nascent RNAs. The resulting bipartite mode of RNA binding can account for previously unexplained observations and may underlie a unifying principle of La function. While a role for hLa in transcription remains controversial, its presence in a Pol III holoenzyme suggests a role reminiscent of the CTD of Pol II, as an integrator of transcriptional and posttranscriptional activities that include 5Ј-and 3Ј-RNA metabolism. Evidence that the 5Ј-end-RNA recognition activity of hLa can be modulated by phosphorylation provides mechanistic insight into the signal transduction function of this protein.La was first described as a human autoantigen more than 20 years ago and has since been identified in many eukaryotes from yeasts to humans (79,143). La has been implicated in several cellular and viral RNA-associated processes, the most ubiquitous of which is the binding to and stabilization of newly synthesized RNA polymerase (Pol) III transcripts (6,17,41,44,58,67,88,103,143,153,154). These transcripts are the precursors to tRNAs, 5S rRNA, U6 snRNA, 7SL (SRP) RNA, 7SK snRNA, hY scRNAs, 4.5S I RNA, B1-Alu, Alu RNAs, and other RNAs (24,43,76,81,86,89,[113][114][115]. Binding occurs via the common UUU-OH 3Ј-terminal motif which results from transcription termination within the Pol III termination signal, oligo(dT) (58,89,113,115,136). As a result of UUU-OH binding and other activities, human La (hLa) also appears to function in transcription termination and reinitiation by Pol III (29, 42, 44-47, 87, 88), although this remains controversial (43,82,146,154).La proteins have been differentially expanded in the mass and domain complexity of their C-terminal domains (CTD) and utilize different pathways of nuclear import in different species. La protein of the yeast Saccharomyces cerevisiae is imported into the nucleus via a pathway that is different from the pathway used by the fission yeast, Schizosaccharomyces pombe, and higher eukaryotes (117). The type of nuclear localization signal (NLS) as well as the transp...

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Efficient synthesis, termination and release of RNA polymerase III transcripts in Xenopusextracts depleted of La protein

Cited by 43 publications

References 50 publications

Human La is found at RNA polymerase III-transcribed genes in vivo

Human La is found at RNA polymerase III-transcribed genes in vivo

The trials and travels of tRNA: Figure 1.

Recognition of Nascent RNA by the Human La Antigen: Conserved and Divergent Features of Structure and Function

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