Promoting Formation of the Heterodimer

To identify genes that may affect heterodimer formation or stability, we screened for mutations in genes other than those encoding tubulin but that behave as does tub1-724. This approach identified null alleles in four distinct genes. Each of these non-essential genes had been previously discovered in screens for microtubule phenotypes but their functions had not been characterized. The detailed phenotypes of these mutations indicate that their role likely involves promoting formation of the heterodimer. This hypothesis is supported by the fact that overexpression of a wild type version of three of these genes partially suppresses tub1-724 . The findings suggest that these genes can participate in a catalyzed pathway for heterodimer formation. It can not be the primary pathway for heterodimer formation, since cells deleted for these genes even in pairwise combinations are viable, but they may represent a salvage pathway promoting reassociation of dissociated heterodimers.