Phosphorylation of spliceosomal protein SAP 155 coupled with splicing catalysis
Abstract
The U2 snRNP component SAP 155 contacts pre-mRNA on both sides of the branch site early in spliceosome assembly and is therefore positioned near or at the spliceosome catalytic center. We have isolated a cDNA encoding human SAP 155 and identified its highly related Saccharomyces cerevisiae homolog (50% identity). The carboxy-terminal two-thirds of SAP 155 shows the highest conservation and is remarkably similar to the regulatory subunit A of the phosphatase PP2A. Significantly, SAP 155 is phosphorylated concomitant with or just after catalytic step one, making this the first example of a protein modification tightly regulated with splicing catalysis.
Keywords
Footnotes
-
↵3 These authors contributed equally to this work.
-
↵4 Present address: Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 USA.
-
↵5 Corresponding author.
-
E-MAIL rreed{at}warren.med.harvard.edu; FAX (617) 432-3091.
-
- Received November 14, 1997.
- Accepted March 11, 1998.
- Cold Spring Harbor Laboratory Press
