Role of p53 in the entrainment of mammalian circadian behavior rhythms.

p53 protein plays a role for control of cell proliferation and the induction of apoptosis in normal cells. However, its role in the circadian rhythms that control many physiological functions including locomotor behavior remains unknown. The present study examined the locomotors activity rhythms of mice which have homozygous mutations of p53 gene. The period of drinking activity rhythms in p53 knockout (p53 KO) mice became unstable under constant dark. Light pulse causes a big phase shifts at CT15.5-17, when p53 mRNA expression peaks in the suprachiasmatic nucleus (SCN). Furthermore, photic entrainment of p53 KO mice is unusual under light-dark conditions. These findings suggest that p53 is involved in entrainment of the circadian behavioral rhythm.