INMP, a novel intranuclear matrix protein related to the family of intermediate filament-like proteins: molecular cloning and sequence analysis.

An important step in understanding nuclear structure and its function in replication and gene regulation is the cloning and characterisation of nuclear matrix proteins. A full-length cDNA-clone, encoding a novel nuclear matrix protein, was isolated from a (lambda gt11 cDNA library derived from murine macrophages. The antibody used for the screen was raised against a single polypeptide isolated from two-dimensional gel electrophoresis of nuclear matrix preparations. The cDNA encodes a protein of 446 amino acids named INMP for intranuclear matrix protein. INMP displays several salient features, a coiled-coil domain, a leucine zipper, a number of phosphorylation sites and a putative nuclear localisation signal. Sequence homology comparisons indicate that INMP is a unique protein which is evolutionary related to the gene family of intermediate filament-like proteins, especially the nuclear lamins.