A novel splicing factor is an integral component of 200S large nuclear ribonucleoprotein (InRNP) particles
Ast, G.; Goldblatt, D.; Offen, D.; Sperling, J.; Sperling, R.
EMBO Journal 10(2): 425-432
1991
ISSN/ISBN: 0261-4189 PMID: 1991453 Document Number: 379051
In previous studies we have shown that nuclear transcripts of several pre-mRNAs can be released from nuclei of mammalian cells in the form of large nuclear ribonucleoprotein (lnRNP) particles. By electron microscopy, these particles appeared as compact composite structures, 50 nm in diameter, which invariably sedimented at the 200S region in sucrose gradients. In order to identify putative protein splicing factors associated with the 200S lnRNP particles, a panel of monoclonal antibodies directed against these particles were screened for their ability to inhibit splicing of pre-mRNA in vitro. In this study we have focused on a nuclear protein of 88 kd in molecular weight, which is an interal component of the lnRNP complex and is recognized by monoclonal antibodies from a specific clone. This protein has been identified here as a novel splicing factor by, (i) antibody inhibition of splicing in vitro and (ii) depletion of splicing activity from HeLa cell nuclear extract after removing the 88 kd polypeptide by immunoadsorption, and complementation of the depleted activity with an affinity-purified 88 kd antigen. This splicing factor has further been shown to be required for the assembly of an active splicing complex.