Ctf8p is a component of Ctf18-RFC, an alternative replication factor C-like 
complex required for efficient sister chromatid cohesion in Saccharomyces 
cerevisiae. We performed synthetic genetic array (SGA) analysis with a ctf8 
deletion strain as a primary screen to identify other nonessential genes 
required for efficient sister chromatid cohesion. We then assessed proficiency 
of cohesion at three chromosomal loci in strains containing deletions of the 
genes identified in the ctf8 SGA screen. Deletion of seven genes (CHL1, CSM3, 
BIM1, KAR3, TOF1, CTF4, and VIK1) resulted in defective sister chromatid 
cohesion. Mass spectrometric analysis of immunoprecipitated complexes identified 
a physical association between Kar3p and Vik1p and an interaction between Csm3p 
and Tof1p that we confirmed by coimmunoprecipitation from cell extracts. These 
data indicate that synthetic genetic array analysis coupled with specific 
secondary screens can effectively identify protein complexes functionally 
related to a reference gene. Furthermore, we find that genes involved in mitotic 
spindle integrity and positioning have a previously unrecognized role in sister 
chromatid cohesion.