Actin Dosage Lethality Screening in Yeast Mediated by Selective Ploidy Ablation Reveals Links to Urmylation/Wobble Codon Recognition and Chromosome Stability

Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, New York 13210.
G3-Genes Genomes Genetics (Impact Factor: 3.2). 03/2013; 3(3):553-61. DOI: 10.1534/g3.113.005579
Source: PubMed


The actin cytoskeleton exists in a dynamic equilibrium with monomeric and filamentous states of its subunit protein actin. The spatial and temporal regulation of actin dynamics is critical to the many functions of actin. Actin levels are remarkably constant, suggesting that cells have evolved to function within a narrow range of actin concentrations. Here we report the results of screens in which we have increased actin levels in strains deleted for the ~4800 nonessential yeast genes using a technical advance called selective ploidy ablation. We detected 83 synthetic dosage interactions with actin, 78 resulted in reduced growth, whereas in 5 cases overexpression of actin suppressed the growth defects caused by the deleted genes. The genes were highly enriched in several classes, including transfer RNA wobble uridine modification, chromosome stability and segregation, cell growth, and cell division. We show that actin overexpression sequesters a limited pool of eEF1A, a bifunctional protein involved in aminoacyl-transfer RNA recruitment to the ribosome and actin filament cross-linking. Surprisingly, the largest class of genes is involved in chromosome stability and segregation. We show that actin mutants have chromosome segregation defects, suggesting a possible role in chromosome structure and function. Monomeric actin is a core component of the INO80 and SWR chromatin remodeling complexes and the NuA4 histone modification complex, and our results suggest these complexes may be sensitive to actin stoichiometry. We propose that the resulting effects on chromatin structure can lead to synergistic effects on chromosome stability in strains lacking genes important for chromosome maintenance.

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Available from: David C Amberg, Aug 14, 2014
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    • "Indeed the actin CHI space is large: 238 nonessential genes (Haarer et al. 2007) and 60 essential genes (Haarer et al. 2011). In addition, synthetic dosage lethality screens with actin (1N+1 gene) against the nonessential genes identified 83 interactions (78 negative and 5 positive) and a relatively small overlap with the CHI gene set (Haarer et al. 2013). In all of these screens there is extensive functional enrichment, demonstrating that specific functions and processes are sensitive to actin gene dosage. "
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