Required for underreplication of DNA, which is found in many late replicating euchromatic regions of salivary gland polytene chromosomes (PubMed:11901119, PubMed:12456726, PubMed:30277458). Functions by promoting the localization and retention of Rif1 to active DNA replication forks where Rif1 inhibits replication fork progression (PubMed:30277458). Controls chromatin organization in polytene chromosomes (PubMed:12456726). Interacts (via SNF2-like region) with Rif1. Localizes to the DNA replication forks and heterochromatin in amplifying ovarian follicle cells (PubMed:30277458). Binds to polytene chromosomes from salivary glands. Localized at late-replicating intercalary heterochromatin and pericentric heterochromatin. Colocalizes with many Polycomb Group proteins binding sites on polytene chromosomes. Expressed throughout development. Weakly expressed. Expressed at higher level in embryos and adult females. Expressed both maternally and zygotically. The SNF2-like region is essential for localization to DNA replication forks and for promoting underreplication. It is not required for localization to heterochromatin.