An unusual 5' splice sequence is efficiently utilized in vivo.

The minor adult chicken alpha-globin gene (alpha D) has an intron splicing sequence at the 5' end of the second intron that begins with the dinucleotide G-C rather than the usual G-T. To understand what role this splice sequence plays in the processing and maturation of nuclear RNA to cytoplasmic RNA, we have analyzed the intron processing of the alpha D-globin transcript in both heterologous (monkey) and homologous (chicken) cells using simian virus 40 and retrovirus vectors, respectively. In both cell types, both introns of the alpha D-globin gene are efficiently and precisely removed.