E2F mediates sustained G2 arrest and down-regulation of Stathmin and AIM-1 expression in response to genotoxic stress.
Exposure of cells to genotoxic agents results in activation of checkpoint pathways leading to cell cycle arrest. These arrest pathways allow repair of damaged DNA before its replication and segregation, thus preventing accumulation of mutations. The tumor suppressor retinoblastoma (RB) is required for the G(1)/S checkpoint function. In addition, regulation of the G(2) checkpoint by the tumor suppressor p53 is RB-dependent. However, the molecular mechanism underlying the involvement of RB and its related proteins p107 and p130 in the G(2) checkpoint is not fully understood. We show here that sustained G(2)/M arrest induced by the genotoxic agent doxorubicin is E2F-dependent and involves a decrease in expression of two mitotic regulators, Stathmin and AIM-1. Abrogation of E2F function by dominant negative E2F abolishes the doxorubicin-induced down-regulation of Stathmin and AIM-1 and leads to premature exit from G(2). Expression of the E7 papilloma virus protein, which dissociates complexes containing E2F and RB family members, also prevents the down-regulation of these mitotic genes and leads to premature exit from G(2) after genotoxic stress. Furthermore, genotoxic stress increases the levels of nuclear E2F-4 and p130 as well as their in vivo binding to the Stathmin promoter. Thus, functional complexes containing E2F and RB family members appear to be essential for repressing expression of critical mitotic regulators and maintaining the G(2)/M checkpoint.
Polager
Shirley
S
Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel.
Ginsberg
Doron
D
D016475:3T3 Cells; D000818:Animals; D064127:Aurora Kinases; D001483:Base Sequence; D018797:Cell Cycle Proteins; D004249:DNA Damage; D017931:DNA Primers; D004268:DNA-Binding Proteins; D015536:Down-Regulation / Q000502:physiology*; D050684:E2F Transcription Factors; D050704:E2F4 Transcription Factor; D016195:G2 Phase / Q000502:physiology*; D051379:Mice; D008868:Microtubule Proteins; D010750:Phosphoproteins / Q000502:physiology*; D011494:Protein Kinases / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases; D050777:Stathmin; D014157:Transcription Factors / Q000502:physiology*
D018797:Cell Cycle Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050704:E2F4 Transcription Factor; C493763:E2f4 protein, mouse; D008868:Microtubule Proteins; D010750:Phosphoproteins; D050777:Stathmin; C493994:Stmn1 protein, mouse; D014157:Transcription Factors; D011494:Protein Kinases; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases