TIMELESS protein is known to be essential for normal circadian rhythms. Aging is a deleterious process which affects all the physiological functions of complex organisms including the circadian rhythms. The circadian aging may produce disorganization among the circadian rhythms, arrhythmicity and even, disconnection from the environment, resulting in a detrimental situation to the organism. However, the role of circadian genes on the aging process is poorly understood. In present study, we found TIMELESS was down-regulated in cellular senescence, and further research indicated E2F1 bound to the promotor of TIMELESS and regulated its expression in cellular senescence. Knockdown of TIMELESS accelerated cellular senescence induced by ectopic expression of RasV12, and overexpression of TIMELESS delayed this kind onset of senescence. Meanwhile, micrococcal nuclease assays proved depletion of TIMELESS exacerbated genomic instability at the onset of senescence. Together, our data reveal that TIMELESS plays a role in OIS, which is associated with genome stability changing. (C) 2018 Elsevier Inc. All rights reserved.