Histone and nonhistone proteins from normal and virus-transformed rat thyroid epithelial cells.

The histone and nonhistone nuclear proteins extracted by different methods from nuclei of normal and virus-transformed rat thyroid epithelial cells (FRTL5 cell line) were studied by polyacrylamide gel electrophoresis in acetic acid/urea and in SDS and by autoradiography. The results have shown that some of these proteins have an higher level of phosphorylation in virus-transformed than in normal cells; moreover, an higher amount of three proteins (C, D, and E), which in normal cells are not detectable at least as Coomassie staining, was found. These proteins, extractable with perchloric acid, are suggested to belong to the High Mobility Group (HMG proteins) and to play some regulatory role.