Molecular characterization of the MAN antigens.

Abstract

The nuclear lamina consists of a filamentous network of proteins situated beneath the inner nuclear membrane and apposed to peripheral chromatin. As a consequence of its location, the nuclear lamina has been proposed to be involved in a number of different cellular functions. I have used a human antiserum to further characterize a novel set of nuclear lamina proteins, termed the MAN antigens. These antigens comprise three major polypeptides with relative mobilities of 78, 58 and 40 kDa. During interphase, the MAN antigens co-localized with the lamins at the nuclear periphery, but were absent from intranuclear foci of lamin B. In cells which possessed micronuclei, both the MAN antigens and lamins A/C were observed to segregate within these structures, separate from lamin B. Through mitosis, lamins A/C were seen to disassemble in late prophase and reassemble in telophase. Conversely, lamin B and the MAN antigens began to disassemble only during late prometaphase and then reformed around segregating chromosomes in anaphase, prior to lamins A/C. The human antiserum was used to screen a P19 embryonal carcinoma cDNA expression library for clones which encoded polypeptides immunologically related to the MAN antigens. (Abstract shortened by UMI.)