Figure 6.

Model for Tip-induced SRF activation. The membrane-associated viral oncoprotein Tip engages and activates the Src-family kinase Lck. This interaction is required for STAT3 phosphorylation and for MAL:SRF activation. Signaling flux from Tip:Lck to the RhoGTPases Rac remains to be established (dashed line). Rac promotes a decrease in the G-actin/F-actin ratio and thereby enables nuclear translocation of MAL and coactivation of SRF-dependent gene expression. Tip:Lck is not linked to Ras, MEK1/2, or ERK1/2 and subsequent TCF activation