Phosphorylation of spliceosomal protein SAP 155 coupled with splicing catalysis.
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.
Wang
C
C
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.pende014@mc.duke.edu
Chua
K
K
Seghezzi
W
W
Lees
E
E
Gozani
O
O
Reed
R
R
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D017173:Caenorhabditis elegans / Q000235:genetics; D002384:Catalysis; D016384:Consensus Sequence; D018076:DNA, Complementary / Q000235:genetics; D005800:Genes, Fungal; D015801:Helminth Proteins / Q000737:chemistry; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000737:chemistry; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D012322:RNA Precursors / Q000378:metabolism; D012326:RNA Splicing / Q000502:physiology*; D000072260:RNA Splicing Factors; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D017381:Spliceosomes / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D018076:DNA, Complementary; D015801:Helminth Proteins; D046911:Macromolecular Substances; D010750:Phosphoproteins; D012322:RNA Precursors; D000072260:RNA Splicing Factors; D017413:Ribonucleoprotein, U2 Small Nuclear; C491800:SAP155 protein, S cerevisiae; C112491:SF3B1 protein, human; D029701:Saccharomyces cerevisiae Proteins; D010749:Phosphoprotein Phosphatases