Biology subjects

Dominska, M.

Publications and source records attributed to Dominska, M..

3 recordsLinked to original sources

bioRxiv2019

Cytological and genetic consequences for the progeny of a mitotic catastrophe provoked by Topoisomerase II deficiency.

Topoisomerase II (Top2) removes topological linkages between replicated chromosomes. Top2 inhibition leads to mitotic catastrophe (MC) when cells unsuccessfully try to split their genetic material between the two daughter cells. Herein, we have characterized the fate of these daughter cells in the budding yeast. Clonogenic and microcolony experiments, in combination with vital and apoptotic stains, showed that 75% of daughter cells become senescent in the short term; they are unable to divide but remain alive. Decline in cell vitality then occurred, yet slowly, uncoordinatedly when comparing pairs of daughters, and independently of the cell death mediator Mca1/Yca1. Furthermore, we showed that senescence can be modulated by ploidy, suggesting that gross chromosome imbalances during segregation may account for this phenotype. Indeed, we found that diploid long-term survivors of the MC are prone to genomic imbalances such as trisomies, uniparental disomies and terminal loss of heterozygosity (LOH), the latter affecting the longest chromosome arms.

cell biology↗

bioRxiv2017

High-resolution mapping of heteroduplex DNA formed in UV-induced and spontaneous mitotic recombination events in yeast

Double-stranded DNA breaks (DSBs) can be generated by both endogenous and exogenous agents. In diploid yeast strains, such breaks are usually repaired by homologous recombination (HR), and a number of different HR pathways have been described. An early step for all HR pathways is formation of a heteroduplex, in which a single-strand from the broken DNA molecule pairs with a strand derived from an intact DNA molecule. If the two strands of DNA are not identical, within the heteroduplex DNA (hetDNA), there will be mismatches. In a wild-type strain, these mismatches are removed by the mismatch repair (MMR) system. In strains lacking MMR, the mismatches persist and can be detected by a variety of genetic and physical techniques. Most previous studies involving hetDNA formed during mitotic recombination have been restricted to a single locus with DSBs induced at a defined position by a site-specific endonuclease. In addition, in most of these studies, recombination between repeated genes was examined; in such studies, the sequence homologies were usually less than 5 kb. In the present study, we present a global mapping of hetDNA formed in a UV-treated MMR-defective mlh1 strain. Although about two-thirds of the recombination events were associated with hetDNA with a continuous array of unrepaired mismatches, in about one-third of the events, we found regions of unrepaired mismatches flanking regions without mismatches. We suggest that these discontinuous hetDNAs involve template switching during repair synthesis, repair of a double-stranded DNA gap, and/or Mlh1-independent MMR. Many of our observed events are not explicable by the simplest form of the double-strand break repair (DSBR) model of recombination. We also studied hetDNA associated with spontaneous recombination events selected on chromosomes IV and V in a wild-type strain. The interval on chromosome IV contained a hotspot for spontaneous crossovers generated by an inverted pair of transposable elements (HS4). We showed that HS4-induced recombination events are associated with the formation of very large (>30 kb) double-stranded DNA gaps.

genetics↗

bioRxiv2017

High-resolution mapping of heteroduplex DNA formed during UV-induced and spontaneous mitotic recombination events in yeast

In yeast, DNA breaks are usually repaired by homologous recombination (HR). An early step for HR pathways is formation of a heteroduplex, in which a single-strand from the broken DNA molecule pairs with a strand derived from an intact DNA molecule. If the two strands of DNA are not identical, there will be mismatches within the heteroduplex DNA (hetDNA). In wild-type strains, these mismatches are repaired by the mismatch repair (MMR) system, producing a gene conversion event. In strains lacking MMR, the mismatches persist. Most previous studies involving hetDNA formed during mitotic recombination were restricted to one locus. Below, we present a global mapping of hetDNA formed in the MMR-defective mlh1 strain. We find that many recombination events are associated with repair of double-stranded DNA gaps and/or involve Mlh1-independent mismatch repair. Many of our events are not explicable by the simplest form of the double-strand break repair model of recombination.

genetics↗