PHOSPHORYLATION OF NUCLEAR-PROTEIN IS AN EARLY EVENT IN TGF-BETA-1 ACTION

Transforming growth factor beta (TGFβ) is a family of polypeptides that modulate growth and differentiation. TGFβ exerts its effects on target cells through interaction with specific cell surface receptors, but the signal transduction pathways are as yet largely unresolved. In this study we report that the growth inhibitory action of TGFβ on mink lung CCl 64 cells is associated with a rapid and transient phosphorylation of a number of nuclear proteins. In parallel, a transient expression of the immediate early gene jun B is observed. The expression of jun B can be inhibited by the protein kinase inhibitor H7 and can be augmented by the phosphatase inhibitor okadaic acid. Thus, protein phosphorylation can be a possible mechanism through which TGFβ1 initiates early genomic responses. © 1991.