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Partitioning RS Domain Phosphorylation in an SR Protein through the CLK and SRPK Protein Kinases.
- Source :
-
Journal of Molecular Biology . Aug2013, Vol. 425 Issue 16, p2894-2909. 16p. - Publication Year :
- 2013
-
Abstract
- Abstract: SR proteins are essential splicing factors whose biological function is regulated through phosphorylation of their C-terminal RS domains. Prior studies have shown that cytoplasmic–nuclear translocalization of the SR protein SRSF1 is regulated by multisite phosphorylation of a long Arg-Ser repeat in the N-terminus of the RS domain while subnuclear localization is controlled by phosphorylation of a shorter Arg-Ser repeat along with several Ser-Pro dipeptides in the C-terminus of the RS domain. To better understand how these two kinases partition Arg-Ser versus Ser-Pro specificities, we monitored the phosphorylation of SRSF1 by CLK1 and SRPK1. Although SRPK1 initially binds at the center of the RS domain phosphorylating in an orderly, N-terminal direction, CLK1 makes widespread contacts in the RS domain and generates multiple enzyme–substrate complexes that induce a random addition mechanism. While SRPK1 rapidly phosphorylates N-terminal serines, SRPK1 and CLK1 display similar activities toward Arg-Ser repeats in the C-terminus, suggesting that these kinases may not separate function in a strict linear manner along the RS domain. CLK1 induces a unique gel shift in SRSF1 that is not the result of enhanced Arg-Ser phosphorylation but rather is the direct result of the phosphorylation of several Ser-Pro dipeptides. These prolines are important for binding and phosphorylation of the SR protein by CLK1 but not for the SRPK1-dependent reaction. The data establish a new view of SR protein regulation in which SRPK1 and CLK1 partition activities based on Ser-Pro versus Arg-Ser placement rather than on N- and C-terminal preferences along the RS domain. [Copyright &y& Elsevier]
Details
- Language :
- English
- ISSN :
- 00222836
- Volume :
- 425
- Issue :
- 16
- Database :
- Academic Search Index
- Journal :
- Journal of Molecular Biology
- Publication Type :
- Academic Journal
- Accession number :
- 89343502
- Full Text :
- https://doi.org/10.1016/j.jmb.2013.05.013