Replication-Associated Recombinational Repair: Lessons from Budding Yeast

Abstract

Recombinational repair processes multiple types of DNA lesions. Though best understood in the repair of DNA breaks, recombinational repair is intimately linked to other situations encountered during replication. As DNA strands are decorated with many types of blocks that impede the replication machinery, a great number of genomic regions cannot be duplicated without the help of recombinational repair. This replication-associated recombinational repair employs both the core recombination proteins used for DNA break repair and the specialized factors that couple replication with repair. Studies from multiple organisms have provided insights into the roles of these specialized factors, with the findings in budding yeast being advanced through use of powerful genetics and methods for detecting DNA replication and repair intermediates. In this review, we summarize recent progress made in this organism, ranging from our understanding of the classical template switch mechanisms to gap filling and replication fork regression pathways. As many of the protein factors and biological principles uncovered in budding yeast are conserved in higher eukaryotes, these findings are crucial for stimulating studies in more complex organisms.

Identification of Genes inSaccharomyces cerevisiaethat Are Haploinsufficient for Overcoming Amino Acid Starvation

“…The protein encoded by the MMS4 gene is a subunit of an endonuclease that cleaves recombination intermediates and is involved in recombination and repair ( Bonner and Zhao 2016 ). There is no obvious connection of this gene to GAAC, yet the heterozygous deletion strain is sensitive to all three starvation compounds.…”

SMC5/6: Multifunctional Player in Replication

“…Increasing the ability of cells to resolve joint molecules can suppress formation of X-shaped recombination structures and revert smc5/6 segregation phenotypes [47,71,97]. SMC5/6 may play both a structural and regulatory role, as the Sgs1/Top3/Rmi1 (STR) helicase complex is recruited and SUMOylated by SMC5/6 [98,99,100,101]. Firstly, auto-SUMOylation of the SMC5/6 subunits leads to recruitment of Sgs1 (mediated by two SUMO-interacting motifs on Sgs1) and, secondly, SMC5/6-dependent SUMOylation of STR promotes its helicase function.…”

“…Generally, smc5/6 mutations, causing combined defects in DNA damage tolerance and pausing site replication, lead to recombination-mediated DNA lesions that are, however, invisible to the checkpoints. This results in premature mitosis with interconnected chromatids (that are cut during cytokinesis) and chromosome breakages [99,114,115].…”

Cyclin-dependent kinase modulates budding yeast Rad5 stability during cell cycle

“…However, when replication forks encounter fork-blocking lesions, the resumption of replication only after removal of the fork-blocking lesions would not be practical, as the completion of DNA replication would depend on the repair efficiency. To circumvent this dependency, the DNA damage tolerance (DDT) pathway ensures completion of DNA replication by bypassing unrepaired DNA lesions without removing them, thereby allowing cells to continue growing [ 2 – 4 ].…”