Essential genes in autosomal heterochromatin of Drosophila melanogaster

We are taking two approaches to understanding the structure, function and r egulation of essential genes within Drosophila heterochromatin. In the firs t, we have undertaken a genetic and molecular characterization of essential genes within proximal 3L heterochromatin. The expression of such 'resident ' genes within a heterochromatic environment is paradoxical and poorly unde rstood, given that the same environment can inactivate euchromatic sequence s (position effect variegation, or PEV). A second approach involves the stu dy of the local chromosomal environment of heterochromatic (het) genes, as assayed both biochemically, and via the effects of genetic modifiers of PEV , the latter being putative components important for het gene expression. O ur results to date suggest that the three most proximal genes in 3L heteroc hromatin have key roles in development, and indicate strong effects of comb inations of genetic modifiers of PEV on het gene expression.