Nuclear localization and involvement in DNA synthesis of Sarcophaga prolyl endopeptidase

A specific prolyl endopeptidase (PEP) inhibitor, ZTTA, selectively inhibited DNA synthesis by imaginal discs and cultured embryonic cells of Sarcophaga peregrina (flesh fly). PEP was found to be localized in restricted nuclear regions. Unfertilized eggs were shown to contain a maternal message for PEP and analysis of Sarcophaga embryos at blastdermal stage revealed PEP was localized exclusively in the nuclei. These results suggest that PEP participates in DNA synthesis by, and therefore cell proliferation, of insect cells. This is the first demonstration of a biological function of PEP.