The GINS complex plays an essential role in the initiation of DNA replication, and progression of DNA replication forks. GINS4 is important for GINS complex assembly (PubMed:12730133). GINS complex seems to bind preferentially to single-stranded DNA (By similarity). Component of the GINS complex which is a heterotetramer of gins1/psf1, gins2/psf2, gins3/psf3 and gins4/sld5 (PubMed:12730133). Component of the CMG helicase complex, composed of the mcm2-7 complex, the GINS complex and cdc45 (PubMed:30979826) (Probable). Belongs to the GINS4/SLD5 family.