A Nuclear Envelope-associated Kinase Phosphorylates Arginine-Serine Motifs and Modulates Interactions between the Lamin B Receptor and Other Nuclear Proteins

doi:10.1074/jbc.271.14.8365

A Nuclear Envelope-associated Kinase Phosphorylates Arginine-Serine Motifs and Modulates Interactions between the Lamin B Receptor and Other Nuclear Proteins (*)

From the (1)Laboratory of Biochemistry, Faculty of Chemistry, The Aristotelian University of Thessaloniki, 54006 Thessaloniki, Greece, the
(2)Program of Cell Biology, European Molecular Biology Laboratory, 69117 Heidelberg, Federal Republic of Germany, and the
(3)Department of Basic Sciences, Faculty of Medicine, The University of Crete, 71 110 Heraklion, Crete, Greece

^¶ To whom correspondence should be addressed. Tel.: 30-81-542-070 (Ext. 226); Fax: 30-81-542-112.

Abstract

Previous studies have identified a subassembly of nuclear envelope proteins, termed “the LBR complex.” This complex includes the lamin B receptor protein (LBR or p58), a kinase which phosphorylates LBR in a constitutive fashion (LBR kinase), the nuclear lamins A and B, an 18-kDa polypeptide (p18), and a 34-kDa protein (p34/p32). The latter polypeptide has been shown to interact with the HIV-1 proteins Rev and Tat and with the splicing factor 2 (SF2). Using recombinant proteins produced in bacteria and synthetic peptides representing different regions of LBR, we now show that the LBR kinase modifies specifically arginine-serine (RS) dipeptide motifs located at the nucleoplasmic, NH-terminal domain of LBR and in members of the SR family of splicing factors. Furthermore, we show that the NH-terminal domain of LBR binds to p34/p32, whereas a mutated domain lacking the RS region does not. Phosphorylation of LBR by the RS kinase completely abolishes binding of p34/p32, suggesting that this enzyme regulates interactions among the components of the LBR complex.

Footnotes

↵^§ Recipient of a research bursary granted by the Commission of the European Communities in the framework of the BIOMED 1 program.
↵* This work was supported in part by a grant from the “German-Greek Co-operation in Science and Technology.” The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

This article is dedicated to Stavros and Adamantia Politis.
↵¹ The abbreviations used are:

ER

endoplasmic reticulum

HIV

human immunodeficiency virus

PMSF

phenylmethylsulfonyl fluoride

PAGE

polyacrylamide gel electrophoresis

GST

glutathione S-transferase.
↵²G. Simos, C. Maison, and S. D. Georgatos, unpublished observations.
↵³E. Nikolakaki, J. Meier, G. Simos, and S. D. Georgatos, unpublished observations.
↵⁴E. Nikolakaki, G. Simos, S. D. Georgatos, and T. Giannakouros, unpublished observations.
↵⁵J. Meier, G. Simos, E. Nikolakaki, T. Giannakouros, and S. D. Georgatos, unpublished observations.
- Received October 19, 1995.
- Revision received December 20, 1995.