Cloning and expression of a cDNA covering the complete coding region of the P32 subunit of human pre-mRNA splicing factor SF2.

We have cloned and expressed a cDNA encoding the 32-kDa subunit (P32) of the human pre-mRNA splicing factor, SF2. This cDNA extends beyond the 5'-end of a previously reported cDNA [Krainer et al., Cell 66 (1991) 383-394]. Importantly, our fragment includes an ATG start codon which was absent from the previously reported cDNA, where it was suggested that translation might initiate at a CTG codon instead of at an ATG codon. Using the vaccinia virus (Vv) expression system, we demonstrate that translation starts at the conventional ATG start codon and not at the CTG codon. The protein is synthesized as a pro-protein of 282 amino acids (aa) that is post-translationally processed by removal of the initial 73 aa to a mature protein of 209 aa.