Structure and splice products of the human gene encoding sds22, a putativemitotic regulator of protein phosphatase-1

sds22 is a regulatory subunit of protein phosphatase-l that is required for the completion of mitosis in yeast. It consists largely of 11 tandem leuci ne-rich repeats of 22 residues that are expected to mediate interactions wi th Ether polypeptides, including protein phosphatase-1. In this paper, we r eport on the structure of the human gene encoding sds22, designated PPP1R7. This gene (33 kb) comprises 11 exons, but these do not coincide with the s equences encoding the leucine-rich repeats. Up to six splice variants can b e generated by exon skipping and alternative polyadenylation, as revealed b y expressed sequence tag database analysis, RT-PCR and Northern blot analys is. The sds22 transcripts are expected to encode four different polypeptide s. sds22 alpha(1) corresponds to the variant cloned previously from human b rain [Renouf et al. (1995) FEES Lett. 375, 75-78]. Sds22 beta(1) is truncat ed within the ninth repeat and has a short and different C-terminus. Both v ariants also exist without the sequence corresponding to exon 2, and these are termed sds22 alpha(2) and sds22 beta(2). The 5'-flanking region of PPP1 R7 contains two NF-Y-binding CCAAT boxes near the transcription start site and potential binding sites for the transcription factors c-Myb, Ik-2 and N F-1, which are conserved in the mouse gene.