Abstract
Histone H3 is phosphorylated during the late G2 and mitosis. The phosphorylation is required for proper chromosome condensation and segregation. The mammalian Aurora B kinase, AIM-1, is responsible for the phosphorylation of H3 histone. When cells are exposed to ionizing radiation (IR), the mitotic phosphorylation of histone H3 is transiently suppressed with dependency of the irradiation doses. Here, we have shown that the regulation of AIM-1 kinase activity is involved in this radiation-induced signal transduction pathway. The repression of the kinase activity induced by IR is independent of functions of either ATM and TP53, upstream checkpoint regulators for Cdc2 kinase during G2 phase. A kinase-negative AIM-1 suppresses the mitotic phosphorylation of histone H3 without Cdc2 inactivation. Thus, the appearance of IR-induced G2 arrest is likely as a result of a mixture of these checkpoint signals. [J Radiat Res 44:423 (2003)]
