Identification of novel cell cycle regulators. C.M Pfleger , K.F. Harvey , I.K. Hariharan. MGH Cancer Center, Massachussetts General Hospital, Charlestown, MA.

   During development of metazoan organisms, cell proliferation is regulated by patterning and nutrient-dependent signals. Many of these signals act by controlling progression through the cell cycle. A number of negative regulators of the cell cycle have been identified, such as CDK inhibitors, which ensure fidelity of DNA replication and cell division. The mechanisms by which the cell cycle is controlled in response to developmental and environmental signals are not fully understood and several molecules involved in cell cycle control remain to be identified. Such proteins have a potential link to cancer biology. To identify novel cell cycle regulators, our laboratory has employed a screening approach to identify homozygous mutations in the Drosophila eye that confer a proliferative advantage. The screening method uses the yeast FLP recombinase enzyme to induce homologous recombination at FLP recombinase target (FRT) sites. Clones of tissue will be generated in the eye that are homozygous for the induced mutation (white tissue) as well as clones of wild type (red) tissue, in an otherwise heterozygous animal. The size of the white patches (mutant clones) are compared to the size of the red patches (wild type clones) and mutations that lead to an increase in white tissue over red tissue are retained. All of the autosome arms, particularly 2L, 3L and 3R have been screened in the laboratory and more than 23 independent loci have been identified. These loci are currently being characterised and include genes that play an important role in cell cycle regulation, such as PTEN, the tuberous sclerosis complex genes, Tsc1 and Tsc2, and the F-Box WD repeat protein, Archipelago. This poster describes results of screening chromosome arm 2R. Five complementation groups that have a white over red mosaic eye, as well as two complementation groups that have an altered proliferation effect have been identified and preliminary characterisation of these has begun.