FUNCTION AND EXPRESSION-REGULATION OF DROSOPHILA DNA REPLICATION ENZY ME GENE

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1. Analyzes of transcriptional regulatory elements of Drosophila PCNA gene using transgenic files : We have established more than 150 independent lines of transgenic files carrying PCNA promoter-lacZ fusion genes having various mutations in the PCNA promoter. Examination of lacZ expression from these transgenic lines during development allowed us to identify three transcriptional regulatory elements (URE : upstrem regulatory elemet, DRE : DNA replication-related element and E2F-recongnition sites). The results indicate that E2F-recognition sites are eddectial for the PCNA gene expression throughout development. DRE is essential in embryos and larvae. URE is essential in various larval tissues.2. Analyzes of functions of regulatory factors for DNA replication enzyme genes using Gal4-targetted expression system : Overexpression of DREF (DRE-binding factor) in Drosophila eye imaginal discs results in abnormal morphogenesis of complex eyes in adolt fly. This is likely caused by ectopic induction of cell proliferation in eye imaginal discs, although detailed machanisms are now under investigation. Overexpression of dominant-negtive form of DRFE in salivary glands inhibited the polytenization of chromosomes. The results indicate that DREF plays an important role in regulation of endoreplization cycles.3. Identification of DREF homologue in species other than Drosophila : Immunoscreeming of Bombyx mori. cDNA library using anti-Drosophila DREF antibody allowed us to pick up several candidate clones for silk worm homologue of DEEF.We are now analyzing nucleotide sequences of these candiate clones. Comparison of structures of DREF between these two species would hopefuly prvide us a clue to identify mammalian homologue of DREF.