Mammalian PRP4 Kinase Copurifies and Interacts with Components of Both the U5 snRNP and the N-CoR Deacetylase Complexes

Abstract

A growing body of evidence supports the coordination of pre-mRNA processing and transcriptional regulation. We demonstrate here that mammalian PRP4 kinase (PRP4K) is associated with complexes involved in both of these processes. PRP4K is implicated in pre-mRNA splicing as the homologue of the Schizosaccharomyces pombe pre-mRNA splicing kinase Prp4p, and it is enriched in SC35-containing nuclear splicing speckles. RNA interference of Caenorhabditis elegans PRP4K indicates that it is essential in metazoans. In support of a role for PRP4K in pre-mRNA splicing, we identified PRP6, SWAP, and pinin as interacting proteins and demonstrated that PRP4K is a U5 snRNP-associated kinase. In addition, BRG1 and N-CoR, components of nuclear hormone coactivator and corepressor complexes, also interact with PRP4K. PRP4K coimmunoprecipitates with N-CoR, BRG1, pinin, and PRP6, and we present data suggesting that PRP6 and BRG1 are substrates of this kinase. Lastly, PRP4K, BRG1, and PRP6 can be purified as components of the N-CoR-2 complex, and affinity-purified PRP4K/N-CoR complexes exhibit deacetylase activity. We suggest that PRP4K is an essential kinase that, in association with the both U5 snRNP and N-CoR deacetylase complexes, demonstrates a possible coordination of pre-mRNA splicing with chromatin remodeling events involved in transcriptional regulation.

We thank Iain Johnstone (University of Glasgow) for use of his C. elegans injection facility, as well as Javier Caceres and Nick Hastie for comments on the manuscript. We acknowledge the aid of Jamal Nasir and Marie-Jose Lafuente in the yeast two-hybrid analysis. Lastly, we thank Robert Lafyatis (Boston University School of Medicine), Masayasu Yamada (Kyoto University), and Stephen Sugrue (University of Florida College of Medicine) for antibodies and plasmid reagents.

G.D. was supported by a fellowship from the Canadian Institutes of Health Research (CIHR), J.T. is supported by an operating grant from the CIHR, H.G.E.S. is supported by a fellowship from the Association for International Cancer Research, and W.A.B. is a Centennial Fellow of the James S. McDonnell Foundation.