An HMG protein, Hmo1, associates with promoters of many ribosomal protein genes and throughout the rRNA gene locus in Saccharomyces cerevisiae.
HMG proteins are architectural proteins that bind to DNA with low sequence specificity, but little is known about their genomic location and biological functions. Saccharomyces cerevisiae encodes 10 HMG proteins, including Hmo1, which is important for maximal transcription of rRNA. Here we use chromatin immunoprecipitation coupled with microarray analysis to determine the genome-wide association of Hmo1. Unexpectedly, Hmo1 binds strongly to the promoters of most ribosomal protein (RP) genes and to a number of other specific genomic locations. Hmo1 binding to RP promoters requires Rap1 and (to a lesser extent) Fhl1, proteins that also associate with RP promoters. Hmo1, like Fhl1 and Ifh1, typically associates with an IFHL motif in RP promoters, but deletion of the IFHL motif has a very modest effect on Hmo1 binding. Surprisingly, loss of Hmo1 abolishes binding of Fhl1 and Ifh1 to RP promoters but does not significantly affect the level of transcriptional activity. These results suggest that Hmo1 is required for the assembly of transcription factor complexes containing Fhl1 and Ifh1 at RP promoters and that proteins other than Fhl1 and Ifh1 also play an important role in RP transcription. Lastly, like mammalian UBF, Hmo1 associates at many locations throughout the rRNA gene locus, and it is important for processing of rRNA in addition to its role in rRNA transcription. We speculate that Hmo1 has a role in coordinating the transcription of rRNA and RP genes.
Hall
Daniel B
DB
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
Wade
Joseph T
JT
Struhl
Kevin
K
D020816:Amino Acid Motifs / Q000235:genetics; D001665:Binding Sites; D051858:Forkhead Transcription Factors; D015966:Gene Expression Regulation, Fungal; D020459:Genes, rRNA / Q000235:genetics*; D006609:High Mobility Group Proteins / Q000378:metabolism*; D006358:Hot Temperature; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012269:Ribosomal Proteins / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
C495776:FHL1 protein, S cerevisiae; D051858:Forkhead Transcription Factors; C103154:HMO1 protein, S cerevisiae; D006609:High Mobility Group Proteins; C440829:RAP1 protein, S cerevisiae; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins; D014157:Transcription Factors