CHARACTERIZATION OF A DROSOPHILA HOMOLOG OF THE 160-KDA SUBUNIT OF THE CLEAVAGE AND POLYADENYLATION SPECIFICITY FACTOR CPSF

Processing of the 3' end of mRNA precursors depends on several protein s. The multisubunit cleavage and polyadenylation specificity factor (C PSF) is required for cleavage of the mRNA precursor as well as polyade nylation. CPSF interacts with the cleavage stimulatory factor complex (CstF), and this interaction increases the specificity of binding. Fol lowing cleavage downstream of the AAUAAA site, CPSF and poly(A) polyme rase (PAP) are required for efficient polyadenylation. Recently, it ha s been shown that 160-kDa subunit of CPSF interacts directly with the 77-kDa subunit of CstF, which is homologous to the product encoded by the Drosophila gene sti(f), and with PAP. Here we report the cloning a nd characterization of a Drosophila homologue of CPSF-160. The 1329-am ino acid dCPSF protein exhibits about 45% and 20% sequence identity, r espectively, to its mammalian and yeast counterparts over its entire l ength. We show that the CPSF homologue is expressed throughout develop ment and that CPSF is essential for viability. Mutations in the cpsf g ene did not alter the phenotype of homozygous su(f) mutations, suggest ing that, for most genes, processing of 3' termini is not sensitive to small changes in cpsf and su(f) dosage.