Rapidly degraded by the proteasome. Cell-cycle regulation with highest expression during the S-phase (at protein level). Over expressed in hepatocytes by drug injury (e.g. DDC; diethyl 1,4-dihydro-2,4,6-trimethyl-3,5-pyridinedicarboxylate). Inducible by the proinflammatory cytokines tumor necrosis factor-alpha (TNFa) and interferon-gamma (IFNg).