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Introduced mutations into the conserved CxxxPxC sequence and the unique LxCxE motif within the C-terminus of JCV tAg. Using a coimmunoprecipitation approach, we confirmed our prediction that the P99A mutant tAg would exhibit a loss of PP2A binding activity. This proline is conserved in the tAgs of primate polyomaviruses as well as of mouse polyoma virus.JCV Small t Protein FunctionsFigure 7. JCV t
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Asmid, pM1o, and 400 ng of one of the following expression vectors that encode JCV early genes under the control of the CMV promoter: pCMV:T+/t+/T9+ (lanes 2, 3; all five tumor proteins expressed), pCMV:T+/t2/T9+ (lanes 4, 5; TAg and 3 T9 proteins expressed) or pCMV:T+/t2/T92 (lanes 6, 7; TAg only expressed). The ability of the proteins produced by the second plasmid to drive replication of the or
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Dies have confirmed this role for JCV TAg as well. Regulation of SV40 DNA replication involves the incompletely understood coordination of TAg phosphorylation and dephosphorylation. Phosphorylation of serines 120 and 123 negatively regulates TAg functions, whereas phosphorylation of threonine 124 is required for TAg-mediated replication [reviewed in 20,21]. Modifications to the corresponding resid