9219371 Rabinow We are studying the structure and function of the Darkener of apricot locus of Drosophila, and two tightly linked functionally related and interacting loci, Rem and Msu. These loci were identified in mutagenic screens for dosage-sensitive modifiers of gene expression. Doa mutants display a maternal effect, are recessive lethal, increase transcription of the copia retrotransposon and alter the expression of a number of host genes, as based upon genetic and morphological criteria. Many of these properties are shared by Rem and Msu, which interact with Doa allele specifically. By sequencing cDNA clones, we found that Doa encodes the Drosophila homologue of murine and human cdc2-like protein kinase (clk). Clk kinase is unusual in that it is structurally related to serine/threonine protein kinases, but auto- phosphorylates on tyrosine residues as well as serines and threonines. We will: 1) Examine the structure/function relationship among Doa, Rem and Msu, whether they are in fact separable genetic loci, and their functional relationship to cdc2 like kinase. 2) Generate antibodies to Doa protein as reagents to determine its intracellular localization and expression during embryonic and imaginal development outside of the eye and eye- antennal imaginal disc. We will also examine Doa mutant embryos to determine the effects of mutations in the kinase on early Drosophila development. 3) Characterize the specificity and substrates of Doa kinase in vitro and in vivo. 4) Determine whether Doa mutations affect mitosis. %%% Our long range goals are to understand the significance and function of dosage-sensitive transcriptional regulators, as one aspect of the regulation of gene expression yielding normal development. Our system provides a unique example for the study of the functions of a dual-specificity kinase in the context of an organism amenable to genetic analysis and which undergoes complex development. ***
