A male-specific 3'-UTR regulates the steady-state level of the exuperantia mRNA during spermatogenesis in Drosophila.

The Drosophila exuperantia gene (exu) functions in both oogenesis and spermatogenesis. Alternative RNA processing and promoter usage generates sex-specific transcripts which differ in their 5' and 3' untranslated regions, but encode the same predicted protein. We have sequenced the breakpoints of an exu allele which is defective in spermatogenesis but functions normally in oogenesis. This allele deletes most of the sequence specific to the male 3'-UTR, together with some flanking DNA, and causes a reduction in steady-state level of exu mRNA in the testis. In addition, we find that a smaller deletion which removes only sequence within the male 3'-UTR reduces the steady-state level of the mRNA and prevents an exu transgene from rescuing male sterility. Males carrying multiple copies of this transgene are fertile, suggesting that the male-specific 3'-UTR functions to maintain a proper level of exu product in the germline.