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J Virol. 1993 Dec;67(12):7556-60.

Adenovirus E4orf4 protein binds to protein phosphatase 2A, and the complex down regulates E1A-enhanced junB transcription.

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  • 1Department of Molecular Biology, Howard Hughes Medical Institute, Princeton University, New Jersey 08544-1014.


Adenovirus E4orf4 protein was previously shown to counteract transactivation of junB by cyclic AMP (cAMP) and E1A protein. It was also shown to cause hypophosphorylation of E1A and c-Fos proteins. Here we show that the E4orf4 protein associates with protein phosphatase 2A. All three subunits of the phosphatase are present in the complex, and the B subunit interacts directly with the viral protein. The complex possesses a phosphatase activity typical of protein phosphatase 2A, and the phosphatase mediates the E4orf4-induced down regulation of junB transcription. Thus, adenovirus E4orf4 protein recruits protein phosphatase 2A into a signal transduction pathway initiated by cAMP and E1A protein.

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