Cyclin L Is an RS Domain Protein Involved in Pre-mRNA Splicing

Liliane A Dickinson,Alasdair J Edgar,Jennifer Ehley,Joel M Gottesfeld

doi:10.1074/jbc.m202266200

Liliane A Dickinson, Alasdair J Edgar + Show 2 more

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https://doi.org/10.1074/jbc.m202266200

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Abstract

We report the cDNA cloning and functional characterization of human cyclin L, a novel cyclin related to the C-type cyclins that are involved in regulation of RNA polymerase II (pol II) transcription. Cyclin L also contains a COOH-terminal dipeptide repeat of alternating arginines and serines, a hallmark of the SR family of splicing factors. We show that recombinant cyclin L interacts with p110 PITSLRE kinase, and that cyclin L antibody co-immunoprecipitates a kinase activity from HeLa nuclear extracts that phosphorylates the carboxyl-terminal domain (CTD) of pol II and splicing factor SC35, and is inhibited by the cdk inhibitor p21. Cyclin L antibody inhibits the second step of RNA splicing in vitro, and recombinant cyclin L protein stimulates splicing under suboptimal conditions. Significantly, the IC(50) for splicing inhibition by p21 is similar to the IC(50) for inhibition of the cyclin L-associated kinase activity. Cyclin L and its associated kinase are thus new members of the pre-mRNA processing machinery.

Highlights

Cyclins and their partners the cyclin-dependent kinases (cdks)1 (reviewed in Refs. 1 and 2) may be classified into two major groups according to their function: the cell cycle regulators, which include the cyclin classes A, B, D, and E and cdks 1, 2, 3, 4, and the transcriptional regulators, comprising the cyclin classes C, H, K, and T and cdks 7, 8, and 9
Cyclins and their partners the cyclin-dependent kinases1 may be classified into two major groups according to their function: the cell cycle regulators, which include the cyclin classes A, B, D, and E and cdks 1, 2, 3, 4, and the transcriptional regulators, comprising the cyclin classes C, H, K, and T and cdks 7, 8, and 9
Cloning of a Novel Cyclin with Homology to the SR Protein Family of mRNA Splicing Factors—A 2076-bp human cyclin L cDNA was cloned by PCR from a human lung cDNA library (GenBankTM accession number AF180920)

Summary

Introduction

Cyclins and their partners the cyclin-dependent kinases (cdks)1 (reviewed in Refs. 1 and 2) may be classified into two major groups according to their function: the cell cycle regulators, which include the cyclin classes A, B, D, and E and cdks 1, 2, 3, 4, and the transcriptional regulators, comprising the cyclin classes C, H, K, and T and cdks 7, 8, and 9. We show that recombinant cyclin L interacts with p110 PITSLRE kinase, and that cyclin L antibody co-immunoprecipitates a kinase activity from HeLa nuclear extracts that phosphorylates the carboxyl-terminal domain (CTD) of pol II and splicing factor SC35, and is inhibited by the cdk inhibitor p21.

Results

Conclusion