Wilhelm bernhard workshop on the cell nucleus

CDC2L5, A NUCLEAR CDC2-RELATED KINASE CONTAINING AN RS DOMAIN IS INVOLVED IN PRE-MRNA SPLICING

Durieux S.#, Even Y., Géraud M.L., Weil D.*, Genevière A.M.

Laboratoire Arago, Université Paris VI-CNRS UMR 7628, Banyuls-sur Mer, France *CNRS UPR1983, Institut André Lwoff, BP8, Villejuif, France
CDC2L5 belongs to a new subgroup of high molecular weight CDC2-like kinases (Marquès et al., 2000). These proteins are characterised by a conserved kinase domain with high similarity with the cyclin-dependent kinases (CDKs). This central domain is surrounded by large sequences displaying conserved motifs among which a sequence rich in serine-arginine residues (RS-domain). RS-domain are frequently found in metazoan proteins involved in pre-mRNA splicing. Northern blotting analysis of CDC2L5 shows that the mRNA is widely yet differentially expressed across a variety of human tissues with the highest expression in liver and placenta. In agreement with the presence of a putative NLS in the N-ter domain, the CDC2L5 protein is expressed in the nucleus of human cultured cells: HeLa, HEK 293 and U2 OS. The CDC2L5 subnuclear distribution is cell cycle dependent. To identify cellular proteins capable of interacting with CDC2L5 a two-hybrid screen was designed in yeast using the full-length CDC2L5 ORF as bait and a human liver cDNA library. Eight clones fulfilling the criteria for interaction of gene products were sequenced and checked against the GenBank-EMBL database. All of them encoded full-length or partial sequences of the same ASF/SF2 splicing factor binding protein. Confirmation of the interaction was provided by coimmunoprecipitation from HeLa cell lysates. A yeast two-hybrid mapping indicates that the N-terminal RS motif containing domain is responsible for this interaction. Moreover overexpression of a CDC2L5 N-terminal domain in transiently transfected HeLa cells severely inhibits the maturation of lymphotoxin transcripts. The above results strongly argue for a role of CDC2L5 in the regulation of premessenger RNA splicing. In that case, CDC2L5 would be the first example of a kinase of the Cdk type involved in the control of gene expression at the mRNA maturation step.

This work was supported by grants from the Association pour la Recherche sur le Cancer (contract n° 5290) and the Ligue contre le Cancer (Pyrénées orientales).

#S. Durieux was recipient of a fellowship from the Fondation Singer-Polignac