A novel DNA nuclease is stimulated by association with the GINS complex

Chromosomal DNA replication requires the spatial and temporal coordination of the activities of several complexes that constitute the replisome. A previously uncharacterized protein, encoded by TK1252 in the archaeon Thermococcus kodakaraensis, was shown to stably interact with the archaeal GINS complex in vivo, a central component of the archaeal replisome. Here, we document that this protein (TK1252p) is a processive, single-strand DNA-specific exonuclease that degrades DNA in the 5′ → 3′ direction. TK1252p binds specifically to the GINS15 subunit of T. kodakaraensis GINS complex and this interaction stimulates the exonuclease activity in vitro. This novel archaeal nuclease, designated GINS-associated nuclease (GAN), also forms a complex in vivo with the euryarchaeal-specific DNA polymerase D. Roles for GAN in replisome assembly and DNA replication are discussed.