Disruption of the circadian clock by a cancer/testis antigen

描述（由申请人提供）：在人类中，夜间轮班工作时暴露在光线下会扰乱正常的昼夜节律，导致癌症发病率增加；然而，支持肿瘤发生中昼夜节律中断的分子机制尚不清楚。人体内几乎每个细胞都有一个内源性分子钟，它以24小时为周期控制整个生化过程。这个分子钟的核心是昼夜基本螺旋-环-螺旋Per:Arnt:Sim转录因子复合物clock:BMAL1，它控制着近15%的基因组的节律性转录，包括代谢、激素分泌和细胞周期的必需基因。在健康的体细胞组织中，生物钟和细胞周期是联系在一起的，因此生物钟限制细胞分裂一次

DESCRIPTION (provided by applicant): In humans, exposure to light at night during shift work disrupts normal circadian rhythms, leading to an increased incidence of cancer; however, the molecular mechanisms underpinning circadian disruption in oncogenesis are not well understood. Nearly every cell in the human body has an endogenous molecular clock that controls integrated biochemical processes on a ~24-hour period. At the core of this molecular clock is the circadian basic helix-loop-helix Per:Arnt:Sim transcription factor complex CLOCK:BMAL1 that controls the rhythmic transcription of nearly 15% of the genome including essential genes in metabolism, hormone secretion and the cell cycle. In healthy somatic tissues the circadian clock and the cell cycle are linked such that the clock gates cell division to once a day thus preventing uncontrolled proliferation. The cell cycle/circadian link has been acknowledged for many years, however, the cellular perturbations that uncouple these two rhythmic systems in cancer remain to be elucidated. The objective of this proposal is to understand how a protein that is not expressed in healthy somatic tissues, yet is upregulated in cancer, represses the circadian clock and the effect of endogenous clock repression on cell proliferation. Our preliminary data show that this cancer-specific protein, PASD1, represses the activity of CLOCK:BMAL1. Based upon preliminary studies, our central hypothesis is that PASD1 silences clock function when expressed in cancer, removing clock-controlled homeostasis and cell cycle gating, leading cells down an oncogenic path. We will examine the role of PASD1 in clock regulation with the following specific aims: 1) Determine the mechanism by which PASD1 represses CLOCK:BMAL1 activity. Preliminary data demonstrate that a region of PASD1 that is conserved with a chromatin targeting domain in CLOCK is required for inhibition of CLOCK:BMAL1 activity. Our working hypothesis is that PASD1 uses molecular mimicry to interfere with the ability of CLOCK:BMAL1 to access target genes at the right time of day. To test this hypothesis we will perform ChIP-seq experiments to examine CLOCK:BMAL1 genomic targeting in the presence and absence of PASD1. 2) Determine how expression of PASD1 modulates circadian cycling and proliferation in human cancer cells. We hypothesize that knockdown of PASD1 in cancer cell lines will improve circadian cycling of CLOCK:BMAL1 target genes, providing more robust rhythms and decreased rates of proliferation. Investigating the mechanism by which a protein that is upregulated in cancer acts directly on the core circadian transcriptional feedback loop will establish a molecular link between circadian disruption and cancer with the long-term goal of identifying cancer therapeutics.