Specific phosphorylation of nuclear non-histone proteins of rat liver after thyreoidectomy and T4 treatment.

The effect of thyroxine (T4) on phosphorylation of non-histone proteins in rat liver nuclei was studied. Non-histone proteins obtained by extracting liver nuclei with 0.4 mol X l-1 KCl from normal (N), hypothyroid (Tx) and Tx rats treated with T4 (100 micrograms kg-1 B.W.), respectively, were incubated with 32P-ATP at 30 degrees C for 5 min followed by sodium dodecyl sulfate-gradient polyacrylamide gel electrophoresis and autoradiographic analysis. Endogenous phosphorylation in Tx rats was decreased. In T4 treated Tx rats phosphorylation of some proteins was recovered, however the 84 X 10(3) mol wt protein was not completely recovered. Phosphorylation of nuclear nonhistone proteins was not altered by the addition cAMP into the incubation. These findings show that in vitro phosphorylation of non-histone proteins of the rat liver nuclei occurs in some specific fractions which may be thyroid hormone dependent.