A Kinase/Phosphatase System Involving the Protooncogene Lck Is Necessary for Inducible Modulation of Sob 1 during T Cell Activation

The phosphotyrosine containing protein Sob 1 regulates inducibility of a DNA binding complex (Band A) at the SRE of c-fosduring T cell activation. In the present study, Sob 1 was regulated by activation of T cells through the T cell antigen receptor. Inhibition of protein tyrosine kinases (PTK) inactivated Sob 1 function and allowed the Band A DNA–protein complex to form. Inhibition of protein tyrosine phosphatases (PTP) caused constitutive activation of Sob 1 function and prevented induction of Band A at the SRE. Thus, Sob 1 is regulated by a constitutive PTP/PTK system. J.CaM 1 cells that lack a functional form of the PTK Lck are unable to induce Band A through the T cell antigen receptor. J.CaM 1 cells reconstituted with Lck seem to induce Band A normally. Thus, functional Lck is required for regulation of Sob 1.