We have identified SGT1 as a dosage suppressor of skp1-4, a mutation causing defects in yeast kinetochore function. Sgt1p physically associates with Skp1p in vivo and in vitro. SGT1 is an essential gene, and different sgt1 conditional mutants arrest with either a G1 or G2 DNA content. Genetic and phenotypic analyses of sgt1-3 (G2 allele) mutants support an essential role in kinetochore function. Sgt1p is required for assembling the yeast kinetochore complex, CBF3, via activation of Ctf13p. Sgt1p also associates with SCF (Skp1p/Cdc53p/F box protein) ubiquitin ligase, sgt1-5 (G1 allele) mutants are defective in Sic1p turnover in vivo and Cln1p ubiquitination in vitro. Human SGT1 rescues an sgt1 null mutation, suggesting that the function of SGT1 is conserved in evolution.
Kitagawa, K., Skowyra, D., Elledge, S. J., Harper, J. W., & Hieter, P. (1999). SGT1 encodes an essential component of the yeast kinetochore assembly pathway and a novel subunit of the SCF ubiquitin ligase complex. Molecular Cell, 4(1), 21–33. https://doi.org/10.1016/S1097-2765(00)80184-7