Characterization of cyclin L2, a novel cyclin with an arginine/serine-rich domain: phosphorylation by DYRK1A and colocalization with splicing factors

J Biol Chem. 2004 Feb 6;279(6):4612-24. doi: 10.1074/jbc.M310794200. Epub 2003 Nov 17.

Abstract

A novel method employing filter arrays of a cDNA expression library for the identification of substrates for protein kinases was developed. With this technique, we identified a new member of the cyclin family, cyclin L2, as a substrate of the nuclear protein kinase DYRK1A. Cyclin L2 contains an N-terminal cyclin domain and a C-terminal arginine/serine-rich domain (RS domain), which is a hallmark of many proteins involved in pre-mRNA processing. The gene for cyclin L2 encodes the full-length cyclin L2, which is predominantly expressed in testis, as well as a truncated splicing variant (cyclin L2S) that lacks the RS domain and is ubiquitously expressed in human tissues. Full-length cyclin L2, but not cyclin L2S, was associated with the cyclin-dependent kinase PITSLRE. Cyclin L2 interacted with splicing factor 2 in vitro and was co-localized with the splicing factor SC35 in the nuclear speckle compartment. Photobleaching experiments showed that a fusion protein of green fluorescent protein and cyclin L2 in nuclear speckles rapidly exchanged with unbleached molecules in the nucleus, similar to other RS domain-containing proteins. In striking contrast, the closely related green fluorescent protein-cyclin L1 was immobile in the speckle compartment. DYRK1A interacted with cyclin L2 in pull-down assays, and overexpression of DYRK1A stimulated phosphorylation of cyclin L2 in COS-7 cells. These data characterize cyclin L2 as a highly mobile component of nuclear speckles and suggest that DYRK1A may regulate splicing by phosphorylation of cyclin L2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arginine / chemistry
  • Base Sequence
  • COS Cells
  • Cell Nucleus / metabolism
  • Cyclins / chemistry*
  • Cyclins / genetics
  • Cyclins / metabolism*
  • DNA, Complementary / genetics
  • Humans
  • In Vitro Techniques
  • Male
  • Mice
  • Molecular Sequence Data
  • Phosphorylation
  • Protein Structure, Tertiary
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / metabolism*
  • RNA Splicing
  • Rats
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Serine / chemistry
  • Substrate Specificity
  • Transcription Factors

Substances

  • CCNL2 protein, human
  • Cyclins
  • DNA, Complementary
  • Recombinant Fusion Proteins
  • Transcription Factors
  • Serine
  • Arginine
  • Dyrk kinase
  • Protein-Tyrosine Kinases
  • Protein-Serine-Threonine Kinases