PMID:20608984

Citation	Sarkar, S, Haldar, S, Hajra, S and Sinha, P (2010) The budding yeast protein Sum1 functions independently of its binding partners Hst1 and Sir2 histone deacetylases to regulate microtubule assembly. FEMS Yeast Res. 10:660-73
Abstract	The budding yeast protein Sum1 is a transcription factor that associates with the histone deacetylase Hst1p or, in its absence, with Sir2p to form repressed chromatin. In this study, SUM1 has been identified as an allele-specific dosage suppressor of mutations in the major alpha-tubulin-coding gene TUB1. When cloned in a 2mu vector, SUM1 suppressed the cold-sensitive and benomyl-hypersensitive phenotypes associated with the tub1-1 mutation. The suppression was Hst1p- and Sir2p-independent, suggesting that it was not mediated by deacetylation events associated with Sum1p when it functions along with its known partner histone deacetylases. This protein was confined to the nucleus, but did not colocalize with the microtubules nor did it bind to alpha- or beta-tubulin. Cells deleted of SUM1 showed hypersensitivity to benomyl and cold-sensitive growth, phenotypes exhibited by mutants defective in microtubule function and cytoskeletal defects. These observations suggest that Sum1p is a novel regulator of microtubule function. We propose that as a dosage suppressor, Sum1p promotes the formation of microtubules by increasing the availability of the alphabeta-heterodimer containing the mutant alpha-tubulin subunit.
Links	PubMed Online version:10.1111/j.1567-1364.2010.00655.x
Keywords	Benomyl/toxicity; Cold Temperature; Gene Deletion; Gene Dosage; Gene Expression; Microtubules/metabolism; Mutant Proteins/genetics; Mutant Proteins/metabolism; Nuclear Proteins/genetics; Nuclear Proteins/metabolism; Repressor Proteins/genetics; Repressor Proteins/metabolism; Saccharomyces cerevisiae/drug effects; Saccharomyces cerevisiae/growth & development; Saccharomyces cerevisiae/metabolism; Saccharomyces cerevisiae/radiation effects; Saccharomyces cerevisiae Proteins/genetics; Saccharomyces cerevisiae Proteins/metabolism; Silent Information Regulator Proteins, Saccharomyces cerevisiae/metabolism; Sirtuin 2/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
YEAST:SUM1		GO:0005634: nucleus	ECO:0000314:		C		Immunofluorescence revealed that SUM1 was dispersed over the entire nucleus of the cell (Figure 4a).	complete CACAO 12215

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