Browse
Submit Data
Databases
API
Help

Dataset Information

14 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

The nuclear and cytoplasmic activities of RNA polymerase III, and an evolving transcriptome for surveillance.

ABSTRACT: A 1969 report that described biochemical and activity properties of the three eukaryotic RNA polymerases revealed Pol III as highly distinguishable, even before its transcripts were identified. Now known to be the most complex, Pol III contains several stably-associated subunits referred to as built-in transcription factors (BITFs) that enable highly efficient RNA synthesis by a unique termination-associated recycling process. In vertebrates, subunit RPC7(α/β) can be of two forms, encoded by POLR3G or POLR3GL, with differential activity. Here we review promoter-dependent transcription by Pol III as an evolutionary perspective of eukaryotic tRNA expression. Pol III also provides nonconventional functions reportedly by promoter-independent transcription, one of which is RNA synthesis from DNA 3'-ends during repair. Another is synthesis of 5'ppp-RNA signaling molecules from cytoplasmic viral DNA in a pathway of interferon activation that is dysfunctional in immunocompromised patients with mutations in Pol III subunits. These unconventional functions are also reviewed, including evidence that link them to the BITF subunits. We also review data on a fraction of the human Pol III transcriptome that evolved to include vault RNAs and snaRs with activities related to differentiation, and in innate immune and tumor surveillance. The Pol III of higher eukaryotes does considerably more than housekeeping.

SUBMITTER: Kessler AC

PROVIDER: S-EPMC8643620 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

The nuclear RNA polymerase II surveillance system targets polymerase III transcripts.

Project description:A key question in nuclear RNA surveillance is how target RNAs are recognized. To address this, we identified in vivo binding sites for nuclear RNA surveillance factors, Nrd1, Nab3 and the Trf4/5–Air1/2–Mtr4 polyadenylation (TRAMP) complex poly(A) polymerase Trf4, by UV crosslinking. Hit clusters were reproducibly found over known binding sites on small nucleolar RNAs (snoRNAs), pre-mRNAs and cryptic, unstable non-protein-coding RNAs (ncRNAs) ('CUTs'), along with ~642 predicted long anti-sense ncRNAs (asRNAs), ~178 intergenic ncRNAs and, surprisingly, ~1384 mRNAs. Five putative asRNAs tested were confirmed to exist and were stabilized by loss of Nrd1, Nab3 or Trf4. Mapping of micro-deletions and substitutions allowed clear definition of preferred, in vivo Nab3 and Nrd1 binding sites. Nrd1 and Nab3 were believed to be Pol II specific but, unexpectedly, bound many oligoadenylated Pol III transcripts, predominately pre-tRNAs. Depletion of Nrd1 or Nab3 stabilized tested Pol III transcripts and their oligoadenylation was dependent on Nrd1–Nab3 and TRAMP. Surveillance targets were enriched for non-encoded A-rich tails. These were generally very short (1–5 nt), potentially explaining why adenylation destabilizes these RNAs while stabilizing mRNAs with long poly(A) tails.

| S-EPMC3102002 | biostudies-literature

Defining the RNA polymerase III transcriptome: Genome-wide localization of the RNA polymerase III transcription machinery in human cells.

Project description:Our view of the RNA polymerase III (Pol III) transcription machinery in mammalian cells arises mostly from studies of the RN5S (5S) gene, the Ad2 VAI gene, and the RNU6 (U6) gene, as paradigms for genes with type 1, 2, and 3 promoters. Recruitment of Pol III onto these genes requires prior binding of well-characterized transcription factors. Technical limitations in dealing with repeated genomic units, typically found at mammalian Pol III genes, have so far hampered genome-wide studies of the Pol III transcription machinery and transcriptome. We have localized, genome-wide, Pol III and some of its transcription factors. Our results reveal broad usage of the known Pol III transcription machinery and define a minimal Pol III transcriptome in dividing IMR90hTert fibroblasts. This transcriptome consists of some 500 actively transcribed genes including a few dozen candidate novel genes, of which we confirmed nine as Pol III transcription units by additional methods. It does not contain any of the microRNA genes previously described as transcribed by Pol III, but reveals two other microRNA genes, MIR886 (hsa-mir-886) and MIR1975 (RNY5, hY5, hsa-mir-1975), which are genuine Pol III transcription units.

| S-EPMC2877568 | biostudies-literature

A link between nuclear RNA surveillance, the human exosome and RNA polymerase II transcriptional termination.

Project description:In eukaryotes, the production of mature messenger RNA that exits the nucleus to be translated into protein in the cytoplasm requires precise and extensive modification of the nascent transcript. Any failure that compromises the integrity of an mRNA may cause its retention in the nucleus and trigger its degradation. Multiple studies indicate that mRNAs with processing defects accumulate in nuclear foci or 'dots' located near the site of transcription, but how exactly are defective RNAs recognized and tethered is still unknown. Here, we present evidence suggesting that unprocessed ?-globin transcripts render RNA polymerase II (Pol II) incompetent for termination and that this quality control process requires the integrity of the nuclear exosome. Our results show that unprocessed pre-mRNAs remain tethered to the DNA template in association with Pol II, in an Rrp6-dependent manner. This reveals an unprecedented link between nuclear RNA surveillance, the exosome and Pol II transcriptional termination.

| S-EPMC3001075 | biostudies-literature

Protein kinase A regulates RNA polymerase III transcription through the nuclear localization of Maf1.

Project description:Maf1 is an essential and specific mediator of transcriptional repression in the RNA polymerase (pol) III system. Maf1-dependent repression occurs in response to a wide range of conditions, suggesting that the protein itself is targeted by the major nutritional and stress-signaling pathways. We show that Maf1 is a substrate for cAMP-dependent PKA in vitro and is differentially phosphorylated on PKA sites in vivo under normal versus repressing conditions. PKA activity negatively regulates Maf1 function because strains with unregulated high PKA activity block repression of pol III transcription in vivo, and strains lacking all PKA activity are hyperrepressible. Nuclear accumulation of Maf1 is required for transcriptional repression and is regulated by two nuclear localization sequences in the protein. An analysis of PKA phosphosite mutants shows that the localization of Maf1 is affected via the N-terminal nuclear localization sequence. In particular, mutations that prevent phosphorylation at PKA consensus sites promote nuclear accumulation of Maf1 without inducing repression. These results indicate that negative regulation of Maf1 by PKA is achieved by inhibiting its nuclear import and suggest that a PKA-independent activation step is required for nuclear Maf1 to function in the repression of pol III transcription. Finally, we report a previously undescribed phenotype for Maf1 in tRNA gene-mediated silencing of nearby RNA pol II transcription.

| S-EPMC1622776 | biostudies-literature

RNA polymerase III interactome

Project description:Many regulatory proteins and complexes have been identified which influence transcription by RNA polymerase (pol) II with a fine precision. In comparison, only a few regulatory proteins are known for pol III, which transcribes mostly house-keeping and non-coding RNAs. Yet, pol III transcription is precisely regulated under various stress conditions like starvation. We used proteomic approaches and pol III transcription complex components TFIIIC (Tfc6), pol III (Rpc128) and TFIIIB (Brf1) as baits to find identify the potential interactors through mass spectrometry-based proteomics. A large number of proteins were found in the interactome, which includes known chromatin modifiers, factors and regulators of transcription by pol I and pol II.

2019-01-02 | PXD003748 | Pride

Characterization of human RNA polymerase III identifies orthologues for Saccharomyces cerevisiae RNA polymerase III subunits.

Project description:Unlike Saccharomyces cerevisiae RNA polymerase III, human RNA polymerase III has not been entirely characterized. Orthologues of the yeast RNA polymerase III subunits C128 and C37 remain unidentified, and for many of the other subunits, the available information is limited to database sequences with various degrees of similarity to the yeast subunits. We have purified an RNA polymerase III complex and identified its components. We found that two RNA polymerase III subunits, referred to as RPC8 and RPC9, displayed sequence similarity to the RNA polymerase II RPB7 and RPB4 subunits, respectively. RPC8 and RPC9 associated with each other, paralleling the association of the RNA polymerase II subunits, and were thus paralogues of RPB7 and RPB4. Furthermore, the complex contained a prominent 80-kDa polypeptide, which we called RPC5 and which corresponded to the human orthologue of the yeast C37 subunit despite limited sequence similarity. RPC5 associated with RPC53, the human orthologue of S. cerevisiae C53, paralleling the association of the S. cerevisiae C37 and C53 subunits, and was required for transcription from the type 2 VAI and type 3 human U6 promoters. Our results provide a characterization of human RNA polymerase III and show that the RPC5 subunit is essential for transcription.

| S-EPMC134740 | biostudies-literature

The RNA polymerase III transcriptome revealed by genome-wide localization and activity-occupancy relationships.

Project description:RNA polymerase III (Pol III) transcribes small untranslated RNAs, such as tRNAs. To define the Pol III transcriptome in Saccharomyces cerevisiae, we performed genome-wide chromatin immunoprecipitation using subunits of Pol III, TFIIIB and TFIIIC. Virtually all of the predicted targets of Pol III, as well as several novel candidates, were occupied by Pol III machinery. Interestingly, TATA box-binding protein occupancy was greater at Pol III targets than virtually all Pol II targets, and the highly occupied Pol II targets are generally strongly transcribed. The temporal relationships between factor occupancy and gene activity were then investigated at selected targets. Nutrient deprivation rapidly reduced both Pol III transcription and Pol III occupancy of both a tRNA gene and RPR1. In contrast, TFIIIB remained bound, suggesting that TFIIIB release is not a critical aspect of the onset of repression. Remarkably, TFIIIC occupancy increased dramatically during repression. Nutrient addition generally reestablished transcription and initial occupancy levels. Our results are consistent with active Pol III displacing TFIIIC, and with inactivation/release of Pol III enabling TFIIIC to bind, marking targets for later activation. These studies reveal new aspects of the kinetics, dynamics, and targets of the Pol III system.

| S-EPMC299761 | biostudies-literature

Different human TFIIIB activities direct RNA polymerase III transcription from TATA-containing and TATA-less promoters.

Project description:Transcription initiation at RNA polymerase III promoters requires transcription factor IIIB (TFIIIB), an activity that binds to RNA polymerase III promoters, generally through protein-protein contacts with DNA binding factors, and directly recruits RNA polymerase III. Saccharomyces cerevisiae TFIIIB is a complex of three subunits, TBP, the TFIIB-related factor BRF, and the more loosely associated polypeptide beta("). Although human homologs for two of the TFIIIB subunits, the TATA box-binding protein TBP and the TFIIB-related factor BRF, have been characterized, a human homolog of yeast B(") has not been described. Moreover, human BRF, unlike yeast BRF, is not universally required for RNA polymerase III transcription. In particular, it is not involved in transcription from the small nuclear RNA (snRNA)-type, TATA-containing, RNA polymerase III promoters. Here, we characterize two novel activities, a human homolog of yeast B("), which is required for transcription of both TATA-less and snRNA-type RNA polymerase III promoters, and a factor equally related to human BRF and TFIIB, designated BRFU, which is specifically required for transcription of snRNA-type RNA polymerase III promoters. Together, these results contribute to the definition of the basal RNA polymerase III transcription machinery and show that two types of TFIIIB activities, with specificities for different classes of RNA polymerase III promoters, have evolved in human cells.

| S-EPMC316990 | biostudies-literature

Autoregulation of an RNA polymerase II promoter by the RNA polymerase III transcription factor III C (TF(III)C) complex.

Project description:Extra TF(III)C (ETC) sites are chromosomal locations bound in vivo by the RNA polymerase III (Pol III) transcription factor III C (TF(III)C) complex, but are not necessarily associated with Pol III transcription. Although the location of ETC sequences are conserved in budding yeast, and similar sites are found in other organisms, their functions are largely unstudied. One such site, ETC6 in Saccharomyces cerevisiae, lies upstream of TFC6, a gene encoding a subunit of the TF(III)C complex itself. Promoter analysis shows that the ETC6 B-box sequence is involved in autoregulation of the TFC6 promoter. Mutation of ETC6 increases TFC6 mRNA levels, whereas mutation immediately upstream severely weakens promoter activity. A temperature-sensitive mutation in TFC3 that weakens DNA binding of TF(III)C also results in increased TFC6 mRNA levels; however, no increase is observed in mutants of TF(III)B or Pol III subunits, demonstrating a specific role for the TF(III)C complex in TFC6 promoter regulation. Chromatin immunoprecipitation shows an inverse relationship of TF(III)C occupancy at ETC6 versus TFC6 mRNA levels. Overexpression of TFC6 increases association of TF(III)C at ETC6 (and other loci) and results in reduced expression of a TFC6 promoter-URA3 reporter gene. Both of these effects are dependent on the ETC6 B-box. These results demonstrate that the TFC6 promoter is directly regulated by the TF(III)C complex, a demonstration of an RNA polymerase II promoter being directly responsive to a core Pol III transcription factor complex. This regulation could have implications in controlling global tRNA expression levels.

| S-EPMC3100981 | biostudies-literature

Extragenic accumulation of RNA polymerase II enhances transcription by RNA polymerase III.

Project description:Recent genomic data indicate that RNA polymerase II (Pol II) function extends beyond conventional transcription of primarily protein-coding genes. Among the five snRNAs required for pre-mRNA splicing, only the U6 snRNA is synthesized by RNA polymerase III (Pol III). Here we address the question of how Pol II coordinates the expression of spliceosome components, including U6. We used chromatin immunoprecipitation (ChIP) and high-resolution mapping by PCR to localize both Pol II and Pol III to snRNA gene regions. We report the surprising finding that Pol II is highly concentrated approximately 300 bp upstream of all five active human U6 genes in vivo. The U6 snRNA, an essential component of the spliceosome, is synthesized by Pol III, whereas all other spliceosomal snRNAs are Pol II transcripts. Accordingly, U6 transcripts were terminated in a Pol III-specific manner, and Pol III localized to the transcribed gene regions. However, synthesis of both U6 and U2 snRNAs was alpha-amanitin-sensitive, indicating a requirement for Pol II activity in the expression of both snRNAs. Moreover, both Pol II and histone tail acetylation marks were lost from U6 promoters upon alpha-amanitin treatment. The results indicate that Pol II is concentrated at specific genomic regions from which it can regulate Pol III activity by a general mechanism. Consequently, Pol II coordinates expression of all RNA and protein components of the spliceosome.

| S-EPMC2082468 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data