Requirement for the Vasa RNA Helicase ingurkenmRNA Localization

Abstract

Localization of specific mRNAs to distinct sites within theDrosophilaoocyte is an early and key step in establishing the anterior–posterior and dorsal–ventral axes. We describe a new function for the RNA helicase encoded by the “posterior” group genevasa(vas) in control of localization of the mRNA encoded by the “dorsal–ventral” patterning genegurken(grk). Two new ethyl methane sulfonate-induced, female sterile alleles ofvashave been isolated. In these mutantsgrkmRNA fails to become localized properly and GRK protein is barely detectable. Surprisinglyfs(1)K10, a recessive female sterile mutation that results in mislocalization ofGRKmRNA to the anterior end of the oocyte, is epistatic to thesevasalleles. This result demonstrates that GRK protein levels sufficient to dorsalize the egg chamber can accumulate invasmutants, iffs(1)K10is also mutant. Taken together these results suggest that regulation ofGRKmRNA localization normally occurs, directly or indirectly, through the VAS RNA-dependent RNA helicase and may suggest that accumulation of GRK protein normally depends onGRKmRNA localization.