The inability to disassemble Rad51 nucleoprotein filaments   leads to aberrant mitosis and cell death
The proper maintenance of genetic material is essential for the survival of living organisms. One of the main safeguards of genome stability is homologous recombination involved in the faithful repair of DNA double-strand breaks, the restoration of collapsed replication forks, and the bypass of replication barriers. Homologous recombination relies on the formation of Rad51 nucleofilaments which are responsible for the homology-based interactions between DNA strands. Here we demonstrate that without the regulation of these filaments by Srs2 and Rad54, which are known to remove Rad51 from single-stranded and double-stranded DNA respectively, the filaments strongly inhibit damage-associated DNA synthesis during DNA repair. Furthermore, this regulation is essential for cell survival under normal growth conditions as in the srs2? rad54? mutants unregulated Rad51 nucleofilaments cause activation of the DNA damage checkpoint, formation of mitotic bridges and loss of genetic material. These genome instability features may stem from the problems at stalled replication forks as the lack of Srs2 and Rad54 in the presence of Rad51 nucleofilaments impedes cell recovery from replication stress. This study demonstrates that the timely and efficient disassembly of recombination machinery is essential for genome maintenance and cell survival. Overall design: Rad51-specific ChIP-seq. The locus specific accumulation of Rad51 in induced PGAL1-RAD55 srs2? rad54? cells was tested (two biological repeats). PGAL1-RAD55 strains were used as controls (two biological repeats). A strain with an HO-inducible unrepairable double-strand break was also included as a control for the ChIP-seq protocol.