A Molecular Link between the Circadian Clock, DNA Damage Responses, and Oncogene Activation

Abstract

Circadian clocks enhance the efficiency and survival of living things by organizing their behavior and body functions. There has been a long history of research seeking a link between circadian clock and tumorigenesis. Studies of animal models and human tumor samples have revealed that the dysregulation of circadian clocks is an important endogenous factor causing mammalian cancer development. The core circadian clock regulators have been implicated in the control of both the cell cycle and DNA damage responses (DDR). Conversely, several intracellular signaling cascades that play important roles in regulation of the cell cycle and the DDR also contribute to circadian clock regulation. This review describes selected regulatory aspects of circadian clocks, providing evidence of a molecular link of the circadian clocks with cellular DDR. ROS stimulate intracellular MAPK/ERK signaling pathway, which transduces photic signal to zCry1a expression. The light-induced zCRY1a interacts directly with the zCLOCK:zBMAL complex and modifies its transcriptional capacity. Notably, the zCLOCK:zBMAL complex regulates the transcription of a variety of genes involved in cellular stress responses and DDR. UV component of sunlight induces DNA damage. Light-induced ROS and activation of MAPK/ERK pathway also induce expression of a DNA repair enzyme, zPHR. The induced zPHR repairs UV-damaged DNA in a light-dependent manner.