Domain-specific Interactions of Human HP1-type Chromodomain Proteins and Inner Nuclear Membrane Protein LBR*
- From the ‡Departments of Medicine and of Anatomy and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, the ¶Systèmes Moléculaires and Biologie Structurale, Laboratoire de Mineralogie-Cristallographie Paris, (LMCP), CNRS URA09, Université Paris 6 and 7, 4 Place Jussieu, 75252 Paris Cedex 05, France, and the ‖Departement de Biologie Cellulaire, Institut Jacques Monod, CNRS, UniversitéParis 7, 2 Place Jussieu, 75251 Paris Cedex 05, France
Abstract
HP1-type chromodomain proteins self-associate as well as interact with the inner nuclear membrane protein LBR (lamin B receptor) and transcriptional coactivators TIF1α and TIF1β. The domains of these proteins that mediate their various interactions have not been entirely defined. HP1-type proteins are predicted by hydrophobic cluster analysis to consist of two homologous but distinct globular domains, corresponding to the chromodomain and chromo shadow domain, separated by a hinge region. We show here that the chromo shadow domain mediates the self-associations of HP1-type proteins and is also necessary for binding to LBR both in vitro and in the yeast two-hybrid assay. Hydrophobic cluster analysis also predicts that the nucleoplasmic amino-terminal portion of LBR contains two globular domains separated by a hinge region. The interactions of the LBR domains with an HP1-type protein were also analyzed by the yeast two-hybrid and in vitro binding assays, which showed that a portion of the second globular domain is necessary for binding. The modular domain organization of HP1-type proteins and LBR can explain some of the diverse protein-protein interactions at the chromatin-lamina-membrane interface of the nuclear envelope.
Footnotes
-
↵* This work was supported in part by National Institutes of Health Grant CA66974, the March of Dimes Birth Defects Foundation, and United States-France Cooperative Research Grant 9415591 from the National Science Foundation.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵§ Supported in part by a postdoctoral research fellowship from the American Liver Foundation. Present address: Lab. of Developmental Hematopoiesis, Sloan-Kettering Inst. for Cancer Research, New York, NY 10021.
-
↵** Supported by INSERM and by a United States-France cooperative research grant from CNRS.
-
↵‡ An Irma T. Hirschl Scholar. To whom correspondence should be addressed: Dept. of Medicine, College of Physicians and Surgeons, Columbia University, 630 West 168th St., 10th Floor, Rm. 508, New York, NY 10032. Tel.: 212-305-8156; Fax: 212-305-6443; E-mail:hjw14{at}columbia.edu.
-
↵1 The abbreviations used are: HCA, hydrophobic cluster analysis; PAGE, polyacrylamide slab gel electrophoresis; GST, glutathione S-transferase.
-
↵2 I. Callebaut, J.-C. Courvalin, H. J. Worman, and J.-P. Mornon, submitted for publication.
-
- Received March 17, 1997.
- Revision received April 1, 1997.
