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DNA Repair (Amst). 2018 Oct;70:49-54. doi: 10.1016/j.dnarep.2018.08.026. Epub 2018 Aug 23.

Deletion of the DEF1 gene does not confer UV-immutability but frequently leads to self-diploidization in yeast Saccharomyces cerevisiae.

Author information

1
Vavilov Institute of General Genetics, Saint-Petersburg Branch, Russian Academy of Sciences, Saint-Petersburg, 199034, Russia; Department of Genetics, Saint-Petersburg State University, Saint-Petersburg, 199034, Russia; Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
2
Department of Genetics, Saint-Petersburg State University, Saint-Petersburg, 199034, Russia; Center for Data-Intensive Biomedicine and Biotechnology, Skolkovo Institute of Science and Technology, Moscow, 143028, Russia; Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya, 29, Saint-Petersburg, 195251, Russia; Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
3
Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA; Departments of Microbiology and Pathology, Biochemistry and Molecular Biology, Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE, USA. Electronic address: ypavlov@unmc.edu.

Abstract

In yeast Saccharomyces cerevisiae, the DEF1 gene is responsible for regulation of many cellular processes including ubiquitin-dependent degradation of DNA metabolism proteins. Recently it has been proposed that Def1 promotes degradation of the catalytic subunit of DNA polymerase δ at sites of DNA damage and regulates a switch to specialized polymerases and, as a consequence, DNA-damage induced mutagenesis. The idea was based substantially on the severe defects in induced mutagenesis observed in the def1 mutants. We describe that UV mutability of def1Δ strains is actually only moderately affected, while the virtual absence of UV mutagenesis in many def1Δ clones is caused by a novel phenotype of the def1 mutants, proneness to self-diploidization. Diploids are extremely frequent (90%) after transformation of wild-type haploids with def1::kanMX disruption cassette and are frequent (2.3%) in vegetative haploid def1 cultures. Such diploids look "UV immutable" when assayed for recessive forward mutations but have normal UV mutability when assayed for dominant reverse mutations. The propensity for frequent self-diploidization in def1Δ mutants should be taken into account in studies of the def1Δ effect on mutagenesis. The true haploids with def1Δ mutation are moderately UV sensitive but retain substantial UV mutagenesis for forward mutations: they are fully proficient at lower doses and only partially defective at higher doses of UV. We conclude that Def1 does not play a critical role in damage-induced mutagenesis.

KEYWORDS:

DEF1; DNA polymerase switch; Induced mutagenesis; Ploidy; Ubiquitin

PMID:
30172224
PMCID:
PMC6173828
[Available on 2019-10-01]
DOI:
10.1016/j.dnarep.2018.08.026

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