ASSOCIATION OF HNRNP S1 PROTEINS C2 AND D2 WITH VIMENTIN INTERMEDIATEFILAMENTS

S1 proteins A-D are hnRNP proteins which were originally isolated from cell nuclei of various tissues, by selective extraction at pH 4.9 fro m the supernatants of nuclei mildly treated with DNase I or RNase A. I n the present study, a hybridoma was isolated which produced a monoclo nal antibody that reacted specifically with S1 proteins C2 and D2. Whe n the antibody was used in indirect immunofluorescence staining of cul tured cells, it stained, in addition to the nuclei, the cytoskeleton-l ike fibrous structures in the cytoplasm. We demonstrate that the cytos keletal filaments are vimentin intermediate filaments. This is the fir st report on the hnRNP protein-association with cytoskeleton, and will help to clarify cytoplasmic mRNA localization as well as cytoplasmic distribution of hnRNP proteins.