Molecular cloning, developmental expression, and cellular localization of the 70-kDa RPA-1 subunit of Drosophila...

Replication protein A (RPA) is a highly conserved multifunctional heterotrimeric complex, involved in DNA replication, repair, recombination, and possibly transcription. Here, we report the cloning of the gene that codes for the largest subunit of the Drosophila melanogaster RPA homolog, dmRPA70. In situ hybridization showed that dmRPA70 RNA is present in developing embryos during the first 16 cycles. After this point, dm-RPA70 expression is downregulated in cells that enter a G1 phase and exit the mitotic cycle, becoming restricted to brief bursts of accumulation from late G1 to S phase. This pattern of regulated expression is also observed in the developing eye imaginal disc. In addition, we have shown that the presence of cyclin E is necessary and sufficient to drive the expression of dmRPA70 in embryonic cells arrested in G1 but is not required in tissues undergoing endoreduplication. Immunolocalization showed that in early developing embryos, the dmRPA70 protein associates with chromatin from the end of mitosis until the beginning of the next prophase in a dynamic speckled pattern that is strongly suggestive of its association with replication foci.