Hmo1, an HMG-box protein, belongs to the yeast ribosomal DNA transcription system.
Hmo1 is one of seven HMG-box proteins of Saccharo myces cerevisiae. Null mutants have a limited effect on growth. Hmo1 overexpression suppresses rpa49-Delta mutants lacking Rpa49, a non-essential but conserved subunit of RNA polymerase I corresponding to the animal RNA polymerase I factor PAF53. This overexpression strongly increases de novo rRNA synthesis. rpa49-Delta hmo1-Delta double mutants are lethal, and this lethality is bypassed when RNA polymerase II synthesizes rRNA. Hmo1 co-localizes with Fob1, a known rDNA-binding protein, defining a narrow territory adjacent to the nucleoplasm that could delineate the rDNA nucleolar domain. These data identify Hmo1 as a genuine RNA polymerase I factor acting synergistically with Rpa49. As an HMG-box protein, Hmo1 is remotely related to animal UBF factors. hmo1-Delta and rpa49-Delta are lethal with top3-Delta DNA topoisomerase (type I) mutants and are suppressed in mutants lacking the Sgs1 DNA helicase. They are not affected by top1-Delta defective in Top1, the other eukaryotic type I topoisomerase. Conversely, rpa34-Delta mutants lacking Rpa34, a non-essential subunit associated with Rpa49, are lethal in top1-Delta but not in top3-Delta.
Gadal
Olivier
O
Laboratoire de Physio-Génomique, Service de Biochimie et Génétique Moléculaire, CEA/Saclay, Bâtiment 142, F-91191 Gif-sur-Yvette, France.
Labarre
Sylvie
S
Boschiero
Claire
C
Thuriaux
Pierre
P
D000595:Amino Acid Sequence; D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics* / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D015870:Gene Expression; D005800:Genes, Fungal; D006609:High Mobility Group Proteins / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D012318:RNA Polymerase I / Q000235:genetics / Q000378:metabolism; D012331:RNA, Fungal / Q000096:biosynthesis; D012335:RNA, Ribosomal / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D004271:DNA, Fungal; D004275:DNA, Ribosomal; C103154:HMO1 protein, S cerevisiae; D006609:High Mobility Group Proteins; D012331:RNA, Fungal; D012335:RNA, Ribosomal; D029701:Saccharomyces cerevisiae Proteins; D012318:RNA Polymerase I