EXPRESSION PATTERNS OF DNA-REPLICATION ENZYMES AND THE REGULATORY FACTOR DREF DURING DROSOPHILA DEVELOPMENT ANALYZED WITH SPECIFIC ANTIBODIES

Specific antibodies were prepared against Drosophila DNA polymerase ep silon and DREF, a regulatory factor for DNA replication-related genes. Using these antibodies together with those for DNA polymerase alpha a nd proliferating cell nuclear antigen (PCNA), we examined expression p atterns and sub-cellular distributions of these proteins during Drosop hila development. DNA polymerase alpha, epsilon and PCNA proteins were maternally stored in unfertilized eggs and maintained at high levels during embryogenesis. With distinct nuclear localization, proteins wer e observed in embryos at interphase stages throughout the 13 nuclear d ivision cycles, suggesting that they all participate in rapid nuclear DNA replication during these cycles. In contrast, maternal storage of a DREF protein was relatively low and its level increased throughout e mbryogenesis. Strong nuclear staining with the anti-DREF antibody was not observed until the nuclear division cycle 8. Immunostaining of var ious larval tissues from transgenic flies carrying the PCNA gene promo ter-lacZ fusion gene revealed co-expression of DREF, PCNA and lacZ sug gesting that DREF regulates the expression of PCNA gene in these tissu es. In addition, we detected a relatively high level of DREF in adult males as well as females. Since DNA polymerase alpha, epsilon: and PCN A are hardly detectable in adult males, DREF very likely regulates gen es other than those closely linked to DNA replication in adult males.