RACK1 is a functional target of the E1A oncoprotein

The adenoviral E1A proteins have been implicated in promotion of proliferation and transformation, inhibition of differentiation, induction of apoptosis, regulation of transcription, and suppression of tumor growth. The ability of E1A to override the fundamental controls of host cells is based on its ability to physically interact with several cellular proteins. We recently characterized RACK1 as a new E1A-interacting protein. In this report, we show that the extreme N-terminal region of E1A, spanning from aminoacids 1-36, and the conserved WD regions of RACK1 are responsible for this interaction. We also demonstrate that E1A and RACK1 colocalize at the perinuclear membrane in the cells. Furthermore, we provide evidence that E1A is able to antagonize the inhibitory effects of RACK1 on Src activity. These results suggest that RACK1 signaling pathway may be a functional target of E1A, contributing to E1A oncogenic effect in the host cells.