Hmo1, an HMG-box protein, belongs to the yeast ribosomal DNA transcription system

Gadal, Olivier; Labarre, Sylvie; Boschiero, Claire; Thuriaux, Pierre

doi:10.1093/emboj/cdf539

Cited by 106 publications

(150 citation statements)

References 67 publications

(114 reference statements)

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“…In yeast, Hmo1p is thought to be the functional homolog of UBF (Gadal et al 2002). It is tempting to speculate that other nonvertebrate eukaryotic organisms will utilize an abundant, nucleolar Hmo1-like HMG protein to specify NOR structure.…”

Section: Discussionmentioning

confidence: 99%

“…The pol I subunit PAF53 has been shown to contact UBF directly (Hanada et al 1996). The yeast homolog of PAF53, RPA49, interacts with the presumptive yeast homolog of UBF, hmo1p (Gadal et al 2002). Direct contacts between TIF-IA/Rrn3 and UBF have not been described.…”

Section: Org Downloaded Frommentioning

confidence: 99%

“…A role for HMG1-box proteins in rDNA chromatin organization appears to have been conserved throughout evolution. Hmo1p, a nucleolar protein with a single HMG1-box, has some sequence similarity to UBF and strongly enhances rDNA transcription in yeast (Gadal et al 2002). Both UBF and Hmo1 belong to the sequence nonspecific class of HMG1-box proteins (Thomas and Travers 2001).…”

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confidence: 99%

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UBF-binding site arrays form pseudo-NORs and sequester the RNA polymerase I transcription machinery

Mais¹,

Wright²,

Prieto³

et al. 2004

Genes Dev.

163

191

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Human ribosomal genes (rDNA) are located in nucleolar organizer regions (NORs) on the short arms of acrocentric chromosomes. Metaphase NORs that were transcriptionally active in the previous cell cycle appear as prominent chromosomal features termed secondary constrictions that are achromatic in chromosome banding and positive in silver staining. The architectural RNA polymerase I (pol I) transcription factor UBF binds extensively across rDNA throughout the cell cycle. To determine if UBF binding underpins NOR structure, we integrated large arrays of heterologous UBF-binding sequences at ectopic sites on human chromosomes. These arrays efficiently recruit UBF even to sites outside the nucleolus and, during metaphase, form novel silver stainable secondary constrictions, termed pseudo-NORs, morphologically similar to NORs. We demonstrate for the first time that in addition to UBF the other components of the pol I machinery are found associated with sequences across the entire human rDNA repeat. Remarkably, a significant fraction of these same pol I factors are sequestered by pseudo-NORs independent of both transcription and nucleoli. Because of the heterologous nature of the sequence employed, we infer that sequestration is mediated primarily by protein-protein interactions with UBF. These results suggest that extensive binding of UBF is responsible for formation and maintenance of the secondary constriction at active NORs. Furthermore, we propose that UBF mediates recruitment of the pol I machinery to nucleoli independently of promoter elements.[Keywords: RNA polymerase I; ribosomal DNA; nucleolar organiser region; nucleolus; upstream-binding factor] Supplemental material is available at http://www.genesdev.org.

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Section: Discussionmentioning

confidence: 99%

Section: Org Downloaded Frommentioning

confidence: 99%

mentioning

confidence: 99%

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UBF-binding site arrays form pseudo-NORs and sequester the RNA polymerase I transcription machinery

Mais¹,

Wright²,

Prieto³

et al. 2004

Genes Dev.

163

191

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“…Association of Hmo1 with rDNA has been described (Hall et al 2006;Berger et al 2007;Kasahara et al 2007), but apart from the observation that it genetically interacts with the Pol I subunit Rpa49 (Gadal et al 2002), little is known about its function.…”

Section: Hmo1 Is a Structural Component Of Active Rrna Genesmentioning

confidence: 99%

“…Although cells can survive in the absence of Hmo1, they are compromised in their growth. There is genetic evidence that Hmo1 assists Pol I in transcribing rDNA, but the molecular mechanism underlying this phenomenon is not understood (Gadal et al 2002).…”

mentioning

confidence: 99%

Actively transcribed rRNA genes in S. cerevisiae are organized in a specialized chromatin associated with the high-mobility group protein Hmo1 and are largely devoid of histone molecules

Merz¹,

Hondele²,

Goetze³

et al. 2008

Genes Dev.

169

215

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Synthesis of ribosomal RNAs (rRNAs) is the major transcriptional event in proliferating cells. In eukaryotes, ribosomal DNA (rDNA) is transcribed by RNA polymerase I from a multicopy locus coexisting in at least two different chromatin states. This heterogeneity of rDNA chromatin has been an obstacle to defining its molecular composition. We developed an approach to analyze differential protein association with each of the two rDNA chromatin states in vivo in the yeast Saccharomyces cerevisiae. We demonstrate that actively transcribed rRNA genes are largely devoid of histone molecules, but instead associate with the high-mobility group protein Hmo1.[Keywords: Chromatin; transcription; ribosomal DNA] Supplemental material is available at http://www.genesdev.org. Received December 11, 2007; revised version accepted February 29, 2008. In the yeast Saccharomyces cerevisiae (hereafter called yeast), >60% of total cellular transcripts are produced from the ribosomal DNA (rDNA) locus by a specific multiprotein enzyme, RNA Polymerase I (Pol I), and an assorted set of additional transcription factors (Reeder 1999;Moss and Stefanovsky 2002;Russell and Zomerdijk 2006). The basal Pol I transcription machinery has been largely defined and consists of two multiprotein complexes, the upstream activating factor (UAF) , and the core factor (CF) (Keys et al. 1994), as well as the TATA-box-binding protein (TBP) (Steffan et al. 1996).The template of RNA Pol I transcription, the yeast ribosomal RNA (rRNA) genes are located on the right arm of chromosome XII in a tandem array of 150-200 copies (Fig. 1), representing almost 10% of the yeast genome. Each of the repeats contains the Pol I-transcribed 35S rRNA gene (precusor of the 5.8S, 18S, and 25S rRNAs) and the RNA Polymerase III (Pol III)-transcribed 5S rRNA gene (Fig. 1). Three different regulatory DNA elements have been identified within the 35S rRNA gene sequence, two of which are located at the 5Ј end of the 35S rDNA, spanning only ∼170 base pairs (bp) (Musters et al. 1989;Kulkens et al. 1991): the upstream element (UE), which is the binding site for the UAF; and the core promoter (CP), where CF can be recruited (Fig. 1). The third element, called the enhancer (ENH), is located at the 3Ј end of the 35S transcription unit (Fig. 1) and was originally identified as exhibiting a stimulatory effect on Pol I transcription in experiments using episomal reporter systems Warner 1984, 1986). However, this sequence has been shown subsequently to be dispensable for RNA Pol I transcription in the chromosomal context (Wai et al. 2001).In each cell, Pol I-transcribed rDNA coexists in two different chromatin states (Conconi et al. 1989). In these studies, cells were treated with the DNA cross-linking drug psoralen, and it was shown that actively transcribed and transcriptionally inactive rRNA genes differed substantially in their degree of psoralen incorporation. The different migration behavior of the corresponding restriction fragments in agarose gel electrophoresis led to the terms s-ban...

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Polymerase I Transcription

Sáez‐Vasquez¹,

Echeverrı́a²

Regulation of Transcription in Plants

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Hmo1, an HMG-box protein, belongs to the yeast ribosomal DNA transcription system

Cited by 106 publications

References 67 publications

UBF-binding site arrays form pseudo-NORs and sequester the RNA polymerase I transcription machinery

UBF-binding site arrays form pseudo-NORs and sequester the RNA polymerase I transcription machinery

Actively transcribed rRNA genes in S. cerevisiae are organized in a specialized chromatin associated with the high-mobility group protein Hmo1 and are largely devoid of histone molecules

Polymerase I Transcription

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