CLONING OF MDEAH9, A PUTATIVE RNA HELICASE AND MAMMALIAN HOMOLOG OF SACCHAROMYCES-CEREVISIAE SPLICING FACTOR PRP43

Yeast splicing factor Prp43, a DEAH box protein of the putative RNA he licase/RNA-dependent NTPase family, is a splicing factor that function s late in the pre-mRNA splicing pathway to facilitate spliceosome disa ssembly, In this paper we report cDNA cloning and characterization of mDEAH9, an apparent mammalian homologue of Prp43, Amino acid sequence comparison revealed that the two proteins are approximate to 65% ident ical over a 500-aa region spanning the central helicase domain and the C-terminal region, Expression of mDEAH9 in S, cerevisiae bearing a te mperature-sensitive mutation in prp43 was sufficient to restore growth at the nonpermissive temperature, This functional complementation was specific, as mouse mDEAH9 failed to complement mutations in related s plicing factor genes prp16 or prp22, Finally, double label immunofluor escence experiments performed with mammalian cells revealed colocaliza tion of mDEAH9 and splicing factor SC35 in punctate nuclear speckles, Thus, the hypothesis that mDEAH9 represents the mammalian homologue of yeast Prp43 is supported by its high sequence homology, functional co mplementation, and colocalization with a known splicing factor in the nucleus, Our results provide additional support for the hypothesis tha t the spliceosomal machinery that mediates regulated, dynamic changes in conformation of pre-mRNA and snRNP RNAs has been highly conserved t hrough evolution.