Human transcription factors IIIC2, IIIC1 and a novel component IIIC0 fulfil different aspects of DNA binding to various pol III genes

Oettel, Susanne; Härtel, Frauke V.; Kober, Ingo; Iben, Sebastian; Seifart, Klaus H.

doi:10.1093/nar/25.12.2440

Cited by 30 publications

(56 citation statements)

References 41 publications

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“…For human TFIIIC, two fractions, named TFIIIC1 and TFIIIC2, are both necessary to reconstitute full TFIIIC DNA binding and transcriptional activities: TFIIIC2, a multisubunit protein (33,50,56), binds strongly by itself to the B block of tRNA genes, but A block binding and gene transcription require TFIIIC1 (50,55). Furthermore, TFIIIC1 can be chromatographically separated from an additional activity, TFIIIC0, that is able to partially substitute for TFIIIC1 activity (38). The situation is different here, since the 55-95 complex (with possible associated components) is not required for TFIIIC activity.…”

Section: Discussionmentioning

confidence: 99%

A Chimeric Subunit of Yeast Transcription Factor IIIC Forms a Subcomplex with τ95

Manaud

Arrebola

Buffin-Meyer

et al. 1998

Molecular and Cellular Biology

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The multisubunit yeast transcription factor IIIC (TFIIIC) is a multifunctional protein required for promoter recognition, transcription factor IIIB recruitment, and chromatin antirepression. We report the isolation and characterization of TFC7, an essential gene encoding the 55-kDa polypeptide, 55, present in affinity-purified TFIIIC. 55 is a chimeric protein generated by an ancient chromosomal rearrangement. Its C-terminal half is essential for cell viability and sufficient to ensure TFIIIC function in DNA binding and transcription assays. The N-terminal half is nonessential and highly similar to a putative yeast protein encoded on another chromosome and to a cyanobacterial protein of unknown function. Partial deletions of the N-terminal domain impaired 55 function at a high temperature or in media containing glycerol or ethanol, suggesting a link between PolIII transcription and metabolic pathways. Interestingly, 55 was found, together with TFIIIC subunit 95, in a protein complex which was distinct from TFIIIC and which may play a role in the regulation of PolIII transcription, possibly in relation to cell metabolism.In eucaryotic cells, the transcription of a variety of small genes is conducted by RNA polymerase III (PolIII) and requires several auxiliary factors. For yeast tRNA gene (tDNA) activation, preinitiation complexes are assembled in a defined order within and upstream of the transcription unit (18, 27, 52). Transcription factor IIIC (TFIIIC) plays a primary role in this multistep complex assembly by binding to the intragenic promoter elements of tRNA genes (the A and B blocks). Yeast TFIIIC is a remarkably large multisubunit factor made of two protein subassemblies, named A and B, that have distinct DNA binding properties, that can be visualized by electron microscopy in a free or DNA-bound form (46), and that can be cleaved by limited proteolysis (37). The B domain binds tightly to the B block (37) and has been shown to display all the properties of enhancer binding proteins (11). Binding of the A domain to the A block is weaker and mostly B block dependent. Once bound, TFIIIC promotes the binding of transcription factor IIIB (TFIIIB) upstream of the transcription start site (6,26,28,31). The process is similar for yeast 5S RNA gene activation, except that TFIIIC assembly is dependent upon the binding of transcription factor IIIA (TFIIIA) to the internal promoter sequence. TFIIIB by itself does not bind detectably to TATA-less PolIII genes but, once assembled via TFIIIC, interacts intimately with DNA and is sufficient, at least in the yeast system, for directing accurate initiation by PolIII during multiple rounds of transcription in vitro (28, 31). Hence, TFIIIB is the initiation factor required for the activation of all PolIII genes, whereas TFIIIC and TFIIIA act as assembly factors. However, it has been shown that TFIIIC is a multifunctional protein, involved not only in promoter recognition and TFIIIB recruitment but also in the displacement of nucleosomes to relieve the repression of transcrip...

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Section: Discussionmentioning

confidence: 99%

A Chimeric Subunit of Yeast Transcription Factor IIIC Forms a Subcomplex with τ95

Manaud

Arrebola

Buffin-Meyer

et al. 1998

Molecular and Cellular Biology

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“…8). A TFIIIC1 activity purified by conventional chromatography, which may correspond to the four polypeptides, binds cooperatively with both TFIIIC2 and a TFIIIC2/TFIIIA complex, and the footprint displayed by TFIIIC2 and the TFIIIC1 activity on a tRNA gene extends over the A and B boxes (Oettel et al 1997).…”

Section: Human Tfiiic1mentioning

confidence: 99%

Recruitment of RNA polymerase III to its target promoters

Schramm¹,

Hernandez²

2002

Genes Dev.

548

601

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A key step in retrieving the information stored in the complex genomes of eukaryotes involves the identification of transcription units and, more specifically, the recognition of promoter sequences by RNA polymerase. In eukaryotes, the task of recognizing nuclear gene promoters and then transcribing the genes is divided among three highly related enzymes, RNA polymerases I, II, and III. Each of these RNA polymerases is dedicated to the transcription of specific sets of genes, and each depends on accessory factors, the so-called transcription factors, to recognize its cognate promoter sequences.RNA polymerase I is unique among the nuclear RNA polymerases in transcribing only one set of genes, the large, tandemly repeated, ribosomal RNA genes, and thus in having to recognize a single promoter structure. RNA polymerase II transcribes the protein-coding genes (mRNA genes) as well as some small nuclear RNA (snRNA) genes. The RNA polymerase II promoters can be divided into a core region, defined as the minimal region capable of directing transcription in vitro, and a regulatory region. The regulatory regions are highly varied in structure, reflecting the highly varied synthesis patterns of cellular proteins and the need for exquisite and complex regulation of these patterns. The core promoters themselves come in different types that, in mRNA-encoding genes, can contain a TATA box, an initiator, a downstream promoter element, or various combinations thereof. The assembly of a functional RNA polymerase II transcription complex on a promoter consisting of just a TATA box has been extensively studied. All the factors involved in the process have been identified, and much is known about how these factors interact with DNA and with each other to recruit, eventually, RNA polymerase II (for reviews, see Orphanides et al. 1996;Woychik and Hampsey 2002). How RNA polymerase II transcription complexes assemble on TATA-less promoters is, however, not as well understood.RNA polymerase III is dedicated to the transcription of an eclectic collection of genes whose main common features are that they encode structural or catalytic RNAs and that they are, as a rule, shorter than 400 base pairs (bp). This length limit is consistent with the elongation properties of RNA polymerase III, which recognizes a simple run of T residues as a termination signal. The genes transcribed by RNA polymerase III encode RNA molecules involved in fundamental metabolic processes, specifically components of the protein synthesis apparatus and components of the splicing and tRNA processing apparatus, as well as RNAs of unknown function. The RNA polymerase III promoters are more varied in structure than the uniform RNA polymerase I promoters, and yet not as diverse as the RNA polymerase II promoters. They have been divided into three main types, two of which are gene-internal and generally TATA-less, and one of which is gene-external and contains a TATA box. Remarkably, we have a good, and in some cases a very detailed, understanding of how RNA polymerase III ...

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“…Moreover, some components of the TFIIIC1 fraction can bind independently to the termination region (60). These components may correspond to the TFIIIC0 fraction described by Oettel et al (59,61), which itself contains two activities, an activity binding to the terminator region of genes with internal promoters (called TBA) and an activity required specifically for U6 transcription (TFIIIU) (61). Recently, one of the components binding to the VAI terminator region has been identified as NF1, and shown to stimulate multiple round transcription (62).…”

Section: U6 Transcription Can Be Reconstituted By a Combination Of Sgmentioning

confidence: 77%

“…Thus, human TFIIIC activity can be separated chromatographically into two activities, TFIIIC1 and TFIIIC2 (49 -52). TFIIIC2, whose subunits have been cloned (53)(54)(55)(56)(57), corresponds to yeast TFIIIC and is not be required for U6 transcription (58,59). In contrast, TFIIIC1, which is not well characterized, is required for transcription of all classes of RNA polymerase III promoters including U6-type promoters (58,59).…”

Section: U6 Transcription Can Be Reconstituted By a Combination Of Sgmentioning

confidence: 99%

Reconstitution of Transcription from the Human U6 Small Nuclear RNA Promoter with Eight Recombinant Polypeptides and a Partially Purified RNA Polymerase III Complex

Chong¹,

Hernandez

2001

Journal of Biological Chemistry

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The human U6 small nuclear (sn) RNA core promoter consists of a proximal sequence element, which recruits the multisubunit factor SNAP c , and a TATA box, which recruits the TATA box-binding protein, TBP. In addition to SNAP c and TBP, transcription from the human U6 promoter requires two well defined factors. The first is hB؆, a human homologue of the B؆ subunit of yeast TFIIIB generally required for transcription of RNA polymerase III genes, and the second is hBRFU, one of two human homologues of the yeast TFIIIB subunit BRF specifically required for transcription of U6-type RNA polymerase III promoters. Here, we have partially purified and characterized a RNA polymerase III complex that can direct transcription from the human U6 promoter when combined with recombinant SNAP c , recombinant TBP, recombinant hB؆, and recombinant hBRFU. These results open the way to reconstitution of U6 transcription from entirely defined components.The nuclear eucaryotic RNA polymerases cannot recognize their target promoters without the help of transcription factors. In the case of RNA polymerase II, basal transcription from a TATA-containing mRNA promoter can be reconstituted in vitro with a set of recombinant or entirely defined factors, both in Saccharomyces cerevisiae and in mammalian systems (1-4). In the case of RNA polymerase III, however, this has been achieved only in the yeast system, for transcription of the U6 snRNA gene (5).The yeast U6 snRNA promoter consists of a TATA box located upstream of the transcription start site and A and B boxes located downstream of the transcription start site (6, 7). The A and B boxes recruit TFIIIC which, together with the TATA box, then recruit TFIIIB (8). In vitro, however, the yeast U6 snRNA promoter can be transcribed in the absence of the B box and TFIIIC because the TATA box is sufficient to recruit TFIIIB (9, 10). S. cerevisiae TFIIIB is a three-subunit complex consisting of the TATA box-binding protein (TBP) 1 (11), the TFIIB-related factor BRF (TDS4/PCF4) (12-14), and the protein BЉ (TFIIIB90/TFC5/TFC7) (5, 15, 16). All three components have been cloned, and TFIIIB has been reconstituted from recombinant subunits (5). Thus, in the case of the yeast U6 promoter, basal RNA polymerase III transcription can be reconstituted in vitro with recombinant TFIIIB and highly purified RNA polymerase III (5).The human U6 snRNA promoter is, unlike the yeast U6 snRNA promoter, entirely located upstream of the transcription start site (see Ref. 17 and references therein). The core promoter consists of a proximal sequence element and a TATA box, and both elements are required for efficient transcription in vitro. The proximal sequence element recruits a multisubunit complex known as SNAP c (18) or PTF (19), which has been reconstituted from recombinant subunits (20). The TATA box recruits TBP (21, 22). Until recently, however, little was known about which other TFIIIB components were required for human U6 transcription because mammalian TFIIIB was only partially characterized. We recently iso...

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Human transcription factors IIIC2, IIIC1 and a novel component IIIC0 fulfil different aspects of DNA binding to various pol III genes

Cited by 30 publications

References 41 publications

A Chimeric Subunit of Yeast Transcription Factor IIIC Forms a Subcomplex with τ95

A Chimeric Subunit of Yeast Transcription Factor IIIC Forms a Subcomplex with τ95

Recruitment of RNA polymerase III to its target promoters

Reconstitution of Transcription from the Human U6 Small Nuclear RNA Promoter with Eight Recombinant Polypeptides and a Partially Purified RNA Polymerase III Complex

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