Pre-Messenger RNA Processing Factors in the Drosophila Genome

In eukaryotes, messenger RNAs are generated by a process that includes coordinated splicing and 3′ end formation. Factors essential for the splicing of mRNA precursors (pre-mRNA) in eukaryotes have been identified primarily through the study of nuclear extracts derived from mammalian cells and Saccharomyces cerevisiae genetics. Here, we identify homologues of most known pre-mRNA processing factors in the recently completed sequence of the Drosophila genome. The set of proteins required for RNA processing shows remarkably little variation among eukaryotic species, and individual proteins are highly conserved. In general, proteins involved in the mechanics of RNA processing are even more conserved than proteins involved in the interpretation of RNA processing signals. The genome does not appear to contain a gene for the U11 RNA, or for a protein unique to the U11 snRNP, which raises the possibility that the U12-dependent spliceosome functions without U11 in Drosophila.