THE CONSERVED PREMESSENGER RNA SPLICING FACTOR-U2AF FROM DROSOPHILA -REQUIREMENT FOR VIABILITY

The large subunit of the human pre-messenger RNA splicing factor U2 sm all nuclear ribonucleoprotein auxiliary factor (hU2AF65) is required f or spliceosome assembly in vitro. A complementary DNA clone encoding t he large subunit of Drosophila U2AF (dU2AF50) has been isolated. The d U2AF50 protein is closely related to its mammalian counterpart and con tains three carboxyl-terminal ribonucleoprotein consensus sequence RNA binding domains and an amino-terminal arginine- and serine-rich (R/S) domain. Recombinant dU2AF50 protein complements mammalian splicing ex tracts depleted of U2AF activity. Germline transformation of Drosophil a with the dU2AF50 complementary DNA rescues a lethal mutation, establ ishing that the dU2AF50 gene is essential for viability. R/S domains h ave been found in numerous metazoan splicing factors, but their functi on is unknown. The mutation in Drosophila U2AF will allow in vivo anal ysis of a conserved R/S domain-containing general splicing factor.