Identification of an snRNP-associated kinase activity that phosphorylates arginine/serine rich domains typical of splicing factors.
AUTOR(ES)
Woppmann, A
RESUMO
The U1 snRNP-specific 70K protein is one of the few snRNP proteins from higher eukaryotic cells that is phosphorylated in vivo (1,2). Immunoaffinity purified spliceosomal snRNPs (U1, U2, U5, and U4/U6) were tested for their ability to phosphorylate in vitro the U1-specific 70K protein. An snRNP-associated kinase activity which phosphorylates all U1-70K isoelectric variants was identified. Like its in vivo counterpart, this snRNP-associated enzyme phosphorylates solely serine residues of the 70K protein, preferentially utilizing ATP as a phosphodonor. Tryptic phosphopeptide analysis revealed an overlapping set of at least four radiolabeled peptides in the in vivo and in vitro phosphorylated protein, suggesting that the snRNP-associated serine kinase is responsible, at least in part, for the 70K protein phosphorylation observed in vivo. Chymotryptic digestion of in vitro, 32P-labeled 70K protein and in vitro phosphorylation studies with a synthetic peptide, indicated that the multiple 70K phosphorylation sites are limited to a highly charged, C-terminal domain of the protein. In vitro phosphorylation studies with the splicing factor ASF/SF2 and several deletion mutants demonstrated that, similar to the U1-70K protein, the snRNP-associated serine kinase phosphorylates the carboxy terminal RS-rich domain of ASF/SF2. A potential general role for this enzyme in the phosphorylation of splicing factors and its consequences for pre-mRNA splicing regulation are discussed.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=309659Documentos Relacionados
- Arginine/serine repeats are sufficient to constitute a splicing activation domain
- Yeast Pre-mRNA Splicing Requires a Pair of U1 snRNP-Associated Tetratricopeptide Repeat Proteins
- Purification and characterization of a kinase specific for the serine- and arginine-rich pre-mRNA splicing factors.
- A comparison of snRNP-associated Sm-autoantigens: human N, rat N and human B/B'.
- A comparison of the snRNP-associated Sm-autoantigens: human N, rat N and human B/B′