Model for DDB1 effects on regulators of cell cycle, cell survival and proliferation.

<p>Ddb1, as a component of the CUL4-DDB1 ubiquitin ligase complex, may control, among other targets and potentially in an indirect way, the expression and activity of <i>p53 (tp53)</i>. Loss of DDB1 results in enhanced p53 activity. This in turn may cause upregulation of <i>p21</i>^CIP1/WAF1 (<i>cdkn1a)</i>, which again contributes to downregulation of <i>ccnd</i> and <i>ccna</i> in proliferating cells. As a result, the cell cycle is deregulated and the equilibrium shifted from proliferation to apoptosis. Whether DDB1 deficiency contributes to genome instability has not been analyzed in our study.