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.
Mesh Terms:
Amino Acid Sequence, Animals, Cell Nucleolus, DNA, Fungal, DNA, Ribosomal, Gene Deletion, Gene Expression, Genes, Fungal, High Mobility Group Proteins, Molecular Sequence Data, Mutation, RNA Polymerase I, RNA, Fungal, RNA, Ribosomal, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Homology, Amino Acid, Transcription, Genetic
EMBO J.
Date: Oct. 15, 2002
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