Molecular analysis of novel Drosophila gene, Gap69C, encoding a homolog ofADP-ribosylation factor GTPase-activating protein

Adenosine diphosphate-ribosylation factor, ARF1, regulates membrane traffic and structure in the endoplasmic reticulum-Golgi and endosomal systems. Th e ARF activity, in turn, is regulated by the guanine nucleotide exchange fa ctors and GTPase-activating proteins (GAPs), We have cloned by transposon t agging a novel Drosophila gene, Gap69C, coding for a putative homolog of AR F1 GTPase-activating protein. The GAP69C protein shares an extensive simila rity within its N-terminal zinc-finger domain with the rat and yeast homolo gs, This domain is known to be required for ARF-CAP activity. The Gap69C is a single-copy gene producing a major 2.1-kb mRNA throughout development, b ut its amount is decreased in larvae, The eye pigmentation produced by the reporter mini-white gene inserted into the 5' UTR of Gap69C suggests that t he expression of Gap69C is nonuniform. In situ hybridization revealed a hig h level of Gap69C transcripts in the morphogenetic furrow of the eye imagin al disc, where cells are arrested in G(1), Generated by the excision of the P-element, the null allele of Gap69C was found to be viable and fertile an d showed no apparent abnormal phenotype, indicating that Gap69C is not esse ntial for fly development. Analysis of the Drosophila genome sequence revea led the presence of other genes related to Gap69C, We propose that the abse nce of a distinctive phenotype in Gap69C null mutants is attributable to re dundancy with other homologs.