Open AccessDefects in the GINS complex increase the instability of repetitive sequences via a recombination-dependent mechanism
Author(s) -
Malgorzata Jedrychowska,
Milena Denkiewicz-Kruk,
Małgorzata Alabrudzińska,
Adrianna Skoneczna,
Piotr Jonczyk,
Michał Dmowski,
Iwona J. Fijałkowska
Publication year - 2019
Publication title -
plos genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.587
H-Index - 233
eISSN - 1553-7404
pISSN - 1553-7390
DOI - 10.1371/journal.pgen.1008494
Subject(s) - replisome , biology , genome instability , dna replication , genetics , helicase , dna repair , homologous recombination , replication protein a , dna polymerase , dna re replication , microbiology and biotechnology , dna , control of chromosome duplication , dna clamp , eukaryotic dna replication , dna damage , gene , dna binding protein , rna , reverse transcriptase , transcription factor
Faithful replication and repair of DNA lesions ensure genome maintenance. During replication in eukaryotic cells, DNA is unwound by the CMG helicase complex, which is composed of three major components: the Cdc45 protein, Mcm2-7, and the GINS complex. The CMG in complex with DNA polymerase epsilon (CMG-E) participates in the establishment and progression of the replisome. Impaired functioning of the CMG-E was shown to induce genomic instability and promote the development of various diseases. Therefore, CMG-E components play important roles as caretakers of the genome. In Saccharomyces cerevisiae , the GINS complex is composed of the Psf1, Psf2, Psf3, and Sld5 essential subunits. The Psf1-1 mutant form fails to interact with Psf3, resulting in impaired replisome assembly and chromosome replication. Here, we show increased instability of repeat tracts (mononucleotide, dinucleotide, trinucleotide and longer) in yeast psf1-1 mutants. To identify the mechanisms underlying this effect, we analyzed repeated sequence instability using derivatives of psf1-1 strains lacking genes involved in translesion synthesis, recombination, or mismatch repair. Among these derivatives, deletion of RAD52 , RAD51 , MMS2 , POL32 , or PIF1 significantly decreased DNA repeat instability. These results, together with the observed increased amounts of single-stranded DNA regions and Rfa1 foci suggest that recombinational mechanisms make important contributions to repeat tract instability in psf1-1 cells. We propose that defective functioning of the CMG-E complex in psf1-1 cells impairs the progression of DNA replication what increases the contribution of repair mechanisms such as template switch and break-induced replication. These processes require sequence homology search which in case of a repeated DNA tract may result in misalignment leading to its expansion or contraction.