Characterization of the chromatin binding activity of lamina-associated polypeptide (LAP) 2

Previous studies have shown that the first and the second halves of the LAP2 N-terminal nucleoplasmic domain function independently in targeting LAP2 to the nuclear envelope, and that the second half is involved in association with the nuclear lamina. To further define the role of the nucleoplasmic domain, we have examined the targeting and chromatin binding functions of the first half of its N-terminus. Expressed polypeptides comprising residues 1-67 fused to the LAP2 transmembrane sequence were localized in perinuclear aggregates, while a residue within residues 244-296 was involved in the translocation of LAP2 to the nucleus as well as in DNA binding. Deletion of any of these domains resulted in a loss of the nuclear envelope targeting function. These data suggest that multimeric interactions of LAP2 with specific cellular components are required for correct targeting to the nuclear envelope and that the first N-terminus has function which is at least directly involved in chromatin association.