Schematic representation of signaling by HTLV-1 Tax. Schematic representation of signaling by HTLV-1 Tax. Targets for HTLV-1 Tax (center column) and biological effects (right column) are shown. ↑, upregulation; ↓, downregulation; SRF, serum response factor; NF-κB, nuclear factor κB; CREB, cyclic AMP (cAMP) response element-binding protein; Cdk4, cyclin-dependent kinase 4; Cdk6, cyclin-dependent kinase 6; Chk1, checkpoint kinase 1; Chk2, checkpoint kinase 2; DNA pol β, DNA polymerase β; DNA-PK, DNA-dependent protein kinase; ATR, ataxia telangiectasia and Rad3 related; ATM, ataxia telangiectasia mutated; Fox04, forkhead transcription factor FoxO4; MDM2, mouse double minute 2 homolog. Martyn K. White et al. Clin. Microbiol. Rev. 2014; doi:10.1128/CMR.00124-13