Association of nuclear matrix antigens with exon-containing splicing complexes.

• DOI: 10.1083/jcb.127.3.593
• Publication Date: 2004-05-15T00:22:22Z
• Authors: B J Blencowe; J A Nickerson; R Issner; S Penman; P A Sharp
• Keywords: Cell Nucleus; 0301 basic medicine; RNA Splicing; Blotting, Western; Antibodies, Monoclonal; Nuclear Proteins; Antigens, Nuclear; Antigen-Antibody Complex; Exons; Arginine; Ribonucleoproteins, Small Nuclear; Autoantigens; 03 medical and health sciences; RNA Precursors; Serine; Tumor Cells, Cultured; Humans; Female; Nuclear Matrix; Amino Acid Sequence; Microscopy, Immunoelectron; HeLa Cells

mAbs raised against the human nuclear matrix (anti-NM)1 mAbs have been used to investigate the role of nuclear matrix antigens in pre-mRNA processing. The three anti-NM mAbs used in this study recognize antigens that are highly localized to nuclear matrix speckles. Surprisingly, all three of these mAbs preferentially immunoprecipitate splicing complexes containing exon sequences. The anti-NM mAbs efficiently immunoprecipitate the exon product complex but not complexes containing the lariat product after the second step of splicing. Two of the anti-NM mAbs completely inhibit pre-mRNA splicing in vitro. However, none of the anti-NM mAbs appear to recognize factors stably associated with splicing snRNPs. The three anti-NM mAbs predominantly react with distinct high molecular weight antigens, which belong to a class of nuclear proteins that selectively precipitate with Ser-Arg protein-splicing factors in the presence of high Mg2+ concentrations. Immunological, biochemical, and cell biological data indicate that two of the NM antigens are related to the defined set of Ser-Arg proteins. The results suggest the existence of an extended Ser-Arg family as a component of the nuclear matrix.