Sgs1

Sgs1 is a DNA helicase in the budding yeast Saccharomyces cerevisiae and a member of the RecQ helicase family. It is encoded by the SGS1 gene (also known as YLR276C) and is the yeast ortholog of the human Bloom syndrome protein, BLM. Sgs1 plays an important role in maintaining genome stability through multiple pathways involved in DNA replication and repair.

A central function of Sgs1 is its participation in processing recombination intermediates. It forms the STR complex with Top3 and Rmi1 (Sgs1-Top3-Rmi1), which dissolves double Holliday junctions to produce non-crossover products during homologous recombination. This activity helps limit crossover events and preserve genome integrity during mitotic and meiotic recombination. Beyond this, Sgs1 collaborates in long-range DNA end resection at double-strand breaks, working with the nuclease Dna2 and replication protein A (RPA) to generate the 3' single-stranded DNA needed for repair. It also participates in processing replication fork structures and contributes to telomere maintenance and the DNA damage response under replication stress.

Genetic studies show that SGS1 loss leads to increased mitotic recombination, sensitivity to DNA damaging agents, and genome instability, though cells remain viable. Because Sgs1 is the yeast analog of BLM, research on SGS1 informs understanding of RecQ helicases and their roles in genome maintenance across eukaryotes, including humans.