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Hmo1, an HMG‐box protein, belongs to the yeast ribosomal DNA transcription system
Author(s) -
Gadal Olivier,
Labarre Sylvie,
Boschiero Claire,
Thuriaux Pierre
Publication year - 2002
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/cdf539
Subject(s) - transcription (linguistics) , humanities , biology , microbiology and biotechnology , art , philosophy , linguistics
Hmo1 is one of seven HMG‐box proteins of Saccharo myces cerevisiae . Null mutants have a limited effect on growth. Hmo1 overexpression suppresses rpa49‐Δ 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‐Δ hmo1‐Δ 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‐Δ and rpa49‐Δ are lethal with top3‐Δ DNA topoisomerase (type I) mutants and are suppressed in mutants lacking the Sgs1 DNA helicase. They are not affected by top1‐Δ defective in Top1, the other eukaryotic type I topoisomerase. Conversely, rpa34‐Δ mutants lacking Rpa34, a non‐essential subunit associated with Rpa49, are lethal in top1‐Δ but not in top3‐Δ .