Monoclonal antibodies to heterogeneous nuclear RNA-protein complexes. The core proteins comprise a conserved group of related polypeptides.

Hybridomas secreting monoclonal antibodies that react with heterogeneous nuclear ribonucleoprotein (hnRNP) core proteins have been isolated by immunizing BALB/c mice with RNP particles isolated from chicken and screening the fusion products with mouse RNP complexes. The antibodies show varying affinities for the hnRNP core proteins that have been blotted onto nitrocellulose. The majority of the immunoglobulins react with all the core group proteins although several recognize subsets of the hnRNP polypeptides. The clones are specific for different antigenic determinants as shown by their inability to compete with one another for binding sites. A mild proteolytic digestion of hnRNP proteins generates fragments that have uniformly lost 12 kDa and contain the antigenic determinants recognized by several of the monoclonal antibodies. Thus, it appears the core proteins comprise a family of related polypeptides possessing underlying structural similarities. Polypeptides similar in number and molecular weights that have antigenic determinants cross-reactive with those of mouse RNP have been found in a number of organisms, thereby emphasizing their possible common structure and function in higher eukaryotes. No difference in the distribution within the cell of individual or groups of core proteins has so far been detected by indirect immunofluorescence.