The DNA damage response is a cornerstone of genomic stability. The cell utilizes mutiple mechanisms including damage detection, cell cycle regulation, damage repair and apoptosis to keep cell homeostasis. The DNA damage response include several biochemical pathways: first, the recognition and repair of damaged DNA; second, the activation of DNA damage checkpoint, which arrests cell cycle progression so as to provides time for DNA repair and prevention of the transmission of genomic abnormalities to the daughter cells; third, apoptosis, which eliminates serious damaged cells. The double strand break (DSB) is believed to be one of the most severe types of DNA damage, and errors in DSB repair could result in genomic instability that might lead to malignancy. It has been reported recently that constitutive activation of the ATM-Chk2-p53 pathway and phosphorylation of histone H2AX acts as an inducible anti-cancer barrier in the early stages of human tumorigenesis. This ATM-regulated DNA damage response network maintains genomic integrity and delays or prevents cancer by eliciting growth arrest or cell death. In context with a recent report, the ATM-dependent DNA-damage cellular signaling has also been shown to be involved in the integration of human immunodeficiency virus type-1 (HIV-1) into host genomes, and KU55933, a specific ATM inhibitor, attenuated the infection of HIV-1 into host cells. The regulation and mechanisms of the signaling pathways of DSB response, and its role in HIV-1 infection and malignancy genesis were reviewed.