CDK4 and infection: These findings support a model in which: (1) CVA6 infection can arrest at G0/G1 phase by down-regulating CDK4, CDK6 and cyclinD1 and upregulating the P53-P21 and P16 pathway; (2) CVA6 infection can inhibit S phase entry by down-regulating cyclinE and CDK2 expression; (3) CVA6 infection can promote G2/M exit by down-regulating cyclinB1 and CDK1 expression.