RecQ helicase. Like the other members of the RecQ helicase family, Sgs1 is important for DNA repair. In particular, Sgs1 collaborates with other proteins to repair double-strand breaks during homologous recombination in eukaryotes.[2]
Meiosis
The Sgs1(BLM) helicase is an ortholog of the human Bloom syndrome protein. It appears to be a central regulator of most of the recombination events that occur during S. cerevisiaemeiosis.[3] During normal meiosis Sgs1(BLM) is responsible for directing recombination towards the alternate formation of either early non-crossover recombinants (NCOs) or Holliday junction joint molecules, the latter being subsequently resolved as crossovers (COs) (see Figure).[3] The several roles of Sgs1 in meiotic recombination were reviewed by Klein and Symington.[4] Primarily, Sgs1 displaces the strand invasion intermediate that initiates recombination, thus facilitating NCO recombination (see Homologous recombination and Bloom syndrome protein).
Sgs1 also has a role in a pathway leading to CO recombinants. Sgs1 together with
EXO1 and MLH1-MLH3 heterodimer (MutL gamma) define a joint molecule resolution pathway that produces the majority of crossovers in budding yeast, and by inference, in mammals.[5]