Zooming in on the actin gene: genetic interactions of diploid and haploid yeast

Abstract

Actin is one of approximately 1200 essential genes in yeast. It is a structural protein involved in a number of functions throughout the cell, including cell growth, division, motility, exocytosis, and many other important processes. However, since actin is an essential gene, the standard method of knocking out the gene in a haploid yeast to study mutant phenotypes or genetic interactions is not feasible. Instead, we used diploid yeast with one working copy of actin to study the genetic interactions within the cell. With the use of diploids with point mutations in actin, we can begin to look more specifically at the profile of the actin surface to greater understand its structure, function, and interactions as well as study the relationship between the abundant haploid data with the new diploid data. In collaboration with a yeast genetics lab, we studied complex haploinsufficient interactions between 32 actin point mutants and the genes across the yeast genome. We found that different alleles exhibit different genetic interactions, but that both the degree and the identity of the interaction partners are similar for alleles that affect amino acids near each other on the surface of actin. We also compared interactions between the actin mutants in diploid and haploid cells and found important differences in diploid interactions, suggesting diploid mutant genetic screens will be important for understanding complex genetics.