An Adenovirus early region 4 deletion mutant induces G2/M arrest via ATM activation and reduces expression of the mitotic marker phosphorylated (ser10) histone 3.

Adenovirus (Ad) type 5 (Ad5) early region 4 (E4) proteins inhibit the DNA damage response (DDR) including activation of the DDR kinase ATM and its substrates, which can induce G2/M cell cycle arrest. Infection with Ad5 or the E4 deletion mutant H5dl1007 (1007) resulted in the accumulation of post G1 cells with > 2 N cellular DNA content. A greater fraction of cells with 4 N DNA content was observed in 1007 infections compared to Ad5; this population was dependent on activation of ATM. G2/M checkpoint kinases, phosphorylated Chk2 (pChk2), and phosphorylated Cdk1 (pCdk1) were upregulated in 1007 infections, and 1007 showed reduced levels of the mitosis marker phosphorylated (Ser10) histone 3 compared to Ad5. Our results show that E4 mutant activation of ATM induces G2/M arrest via activation of checkpoint kinases, thereby contributing to viral-mediated regulation of the cell cycle.