Two‐Dimensional Analysis of Proteins Associated with Heterogenous Nuclear RNA in Various Animal Cell Lines

Abstract

The protein complement of heterogenous nuclear RNA [hnRNA] .cntdot. protein particles from [human cervical cancer] HeLa, mouse [fibroblast] L and Chinese hamster ovary [CHO] cells was analyzed by 2-dimensional gel electrophoresis using 2 previously reported techniques. Over 100 individual spots were reproducibly detected both in stained gel and in autoradiographs of proteins labeled with L-[35S]methionine. Large similarities, especially in the 25,000-40,000 Mr [relative molecular weight] cluster of basic protein, were found among these 3 mammalian species. Of the phosphoproteins, the bands described by 1-dimensional gels with Mr values of 28,000, 30,000, 37,000 and 52,000 are resolved into about 15 individual spots, suggesting a corresponding number of distinct states of phosphorylation. Phosphoproteins are apparently unrelated to the major basic protein species. Particles of different size classes were analyzed with respect to their content of individual proteins, both non-phosphorylated and phosphorylated. Phosphoproteins become progressively more abundant with particles of increasing size. Some phosphoproteins might belong to a nuclear structure to which hnRNA is normally bound.