Skip to main content


Circadian adaptation to cell injury stresses: a crucial interplay of BMAL1 and HSF1


The circadian clock system confers daily anticipatory physiological processes with the ability to be reset by environmental cues. This “circadian adaptation system” (CAS), driven by cell-autonomous molecular clocks, orchestrates various rhythmic physiological processes in the entire body. Hence, the dysfunction of these clocks exacerbates various diseases, which may partially be due to the impairment of protective pathways. If this is the case, how does the CAS respond to cell injury stresses that are critical in maintaining health and life by evoking protective pathways? To address this question, here we review and discuss recent evidence revealing life-protective (pro-survival) molecular networks between clock (e.g., BMAL1, CLOCK, and PER2) and adaptation (e.g., HSF1, Nrf2, NF-κB, and p53) pathways, which are evoked by various cell injury stresses (e.g., heat, reactive oxygen species, and UV). The CK2 protein kinase-integrated interplay of the BMAL1 (clock) and HSF1 (heat-shock response) pathways is one of the crucial events in CAS.

Why did circadian clock systems evolve? We assume that daily changes in certain stressors on ancient earth, such as strong reactive oxygen species (ROS)-producing solar radiation during the daytime, caused lethal damage and various diseases by ROS-induced genotoxic/proteotoxic stresses, compelling the evolution of such clocks as a daily-regulated protection system. The circadian system, with the ability to undergo adaptive synchronization (resetting) by environmental cues, orchestrates a wide variety of physiological rhythms via global rhythmic gene expression. In mammals, the molecular core of the circadian system consists of clock proteins (BMAL1, CLOCK, CRY1/2, and PER1–3) that operate in transcriptional–translational negative feedback loops [16]. The functions of clock proteins are modulated by protein modification enzymes (e.g., CK1, CK2, CLOCK, and SIRT1) [715]. In this review, we summarize advances in the study of the circadian adaptation system (CAS) in which clock and life-protective (pro-survival; survival-promoting) adaptation (e.g., anti-oxidant, anti-apoptotic, DNA repair, and heat-shock response; HSR) pathways form molecular networks that act against critical environmental stresses (Fig. 1). We also discuss whether circadian clocks are indispensable for life.

Fig. 1

Critical stress reset circadian clocks to evoke life-protection systems. See the text for more details

Responses of circadian clocks to critical stresses

For the maintenance of health and survival in response to critical stresses, such as heat, cold, ROS-producing stimuli, low/high pH, and UV, circadian clocks are synchronized (reset; i.e., each cellular clock phase is shifted), changing the period or amplitude of circadian oscillators. Circadian Per2 rhythms of fibroblasts are synchronized in response to an appropriate level of acute heat shock (43 °C for approximately 30 min) [16]. Longer exposure to heat decreases cultured cell viability. Interestingly, exposure to a warm water bath (41 °C for 2 days) stimulates phase shifts of the peripheral (liver and kidney) circadian clocks in PER2::LUCIFERASE mice [17], with a core body temperature maintained at 40–41 °C. Longer exposure to this high core body temperature (1–3 °C higher than normal) would be critical to the health and survival of mice. From these findings on clock synchronization in response to stress, we hypothesized that appropriate (critical) doses of stresses modulate clock function and synergistically evoke stress-resistant adaptation systems (Fig. 1). In particular, critical oxidative stress (cOS) at the threshold of life and death induced by near-lethal doses of ROS (>1 mM H2O2 for 10 min) resets circadian Per2 rhythms in fibroblasts and U2OS cells [18]. In addition, synergistically, this clock-resetting response evokes pro-survival pathways, such as HSF1 (HSR), Nrf2 (anti-oxidant) and NF-κB, (anti-apoptotic) pathways [18]. In UV-irradiated cells, we observed similar responses (paper in preparation). Extracellular pH levels affect circadian Bmal1 rhythms in Rat-1 fibroblasts. Upon decreasing the pH from 7.5 to 6.2, the period of the rhythm shortens, and the oscillation dampens more rapidly [19]. Regardless of the timing of treatment, alkalinization by changing the pH from 7.0 to 7.4 resets the rhythm, with the trough level being reached at 27.6 ± 0.5 h (examined at CT4, 10, 16, and 22, where CT12 is defined as the trough time points of the rhythm) after the pH shift. In contrast, acidification by changing the pH from 7.0 to 6.6 at the CTs resets the rhythm, with the peak level being reached at 28.6 ± 0.4 h after the treatment. In addition, at low pH (6.7), circadian Bmal1 rhythms in human primary fibroblasts are shortened and show lower amplitude without affecting cell viability [20]. This suggests that pro-survival programs work at pH 6.7 but not at a lower pH. Thus, our hypothesis may be applicable to cases with low pH. However, even several days of hypoxia in free-running rats did not cause any significant phase shift in the circadian pattern [21, 22], indicating that our hypothesis may not be applicable to cases with hypoxia. However, hypoxia affects the amplitude of circadian rhythms via HIF1α-mediated signaling [23].

To address the issue of whether CAS response is dependent on the circadian phase, we first need to show the phase response curve (PRC) of the clock toward each type of stress. However, thus far, only limited information on this has been reported. PRC of clocks in response to UV has been reported [24]. Wild-type mice show a robust response to UV, and the complete PRC to UV light has been described. Phase delays during the early subjective night (CT15 ± 1.5 h) were −127 ± 11 min, and small but significant advances occurred in the late subjective night (CT21 ± 1.5 h = 29 ± 8 min). No effect of UV was found during the subjective day (CT0–CT12) [24]. Regarding critical ROS, heat shock, and UV stresses that can affect cellular clock gene expression rhythms, we have already obtained PRC data suggesting the circadian-phase-dependent responses of CAS (paper in preparation).

Interplay of circadian and adaptive response systems

Next, we focus on the mechanism underlying the abovementioned responses and the involvement of circadian clocks in adaptation to critical stresses. Adaptive response systems are directly activated by these stresses, mostly via intracellular signal transduction pathways (e.g., via activation/modulation by protein modification pathways) [2529]. However, recent findings have revealed that the circadian system modulates (strengthens) the adaptive responsive pathways (Fig. 2) [3034]. In addition, in response to stress, modifying enzymes for clock proteins, such as CK2 protein kinases and SIRT1 deacetylase, may modulate circadian core oscillators [1215].

Fig. 2

The triangle network hypothesis of circadian adaptation systems (CAS). See the text for more details

We hypothesize that the triangular interplay of the three categorized components (pathways or systems) forms the core of CAS (Fig. 2). Circadian–heat-shock response (HSR) crosstalk commonly occurs in response to genotoxic/proteotoxic stresses, such as ROS [18], heat shock [16], and UV (paper in preparation). Therefore, among adaptive response systems as the mediator of a core circadian oscillator, the HSR system is probably crucial for CAS operation. In circadian–HSR crosstalk, HSR triggers clock synchronization, whereas the clock activates HSR systems. Strikingly, CK2 phosphorylates HSF1-Thr142 and BMAL1-Ser90 in response to cOS, which induces interaction between BMAL1 and HSF1 to trigger clock synchronization and synergistic activation of pro-survival signaling pathways [18]. This CK2–BMAL1–HSF1 crosstalk exemplifies the core of the triangular interplay in CAS. CLOCK, EP100, and SIRT1 may also be integrators for CAS [33, 35] by the CLOCK-mediated acetylation of BMAL1-Lys537 [14], EP100-mediated acetylation of HSF1 [36], and SIRT1-mediated deacetylation of BMAL1 [15] and HSF1 [37].

Circadian–HSR crosstalk then evokes various adaptive response pathways. The circadian pathway activates Nrf2-mediated anti-oxidant [18, 38] and NF-κB,-mediated anti-apoptotic and anti-inflammatory [18, 39] pathways, while down-regulating the caspase-3-mediated apoptotic pathway [18]. The HSR pathway up-regulates the p53-mediated anti-oncogenic pathway via the genotoxic stress-induced HSF1–p53 interaction and the subsequent nuclear entry of p53 [40, 41]. In contrast, p53 suppresses the circadian pathway through the p53-mediated blocking of BMAL1–CLOCK binding to the Per2 promoter to suppress Per2 expression [42].

Conclusion and perspective: is the circadian clock indispensable for survival?

In this review, we have summarized advances in the study on the responses of CAS against cell injury stresses and propose a hypothesis explaining how CAS responds to such stresses via the interplay of circadian, adaptive response, and protein modification systems (Fig. 2). Upon exposure to ROS-induced cOS, the circadian system is indispensable for cellular survival. However, the protective role of the clock in multicellular systems, such as tissues/organs and the entire body, remains elusive. If a small population of damaged cells survives without repair through circadian-pathway-evoked pro-survival signals, the propagation of these surviving damaged cells may cause various diseases, such as cancer. In contrast, circadian–HSR crosstalk can evoke repair pathways, e.g., via p53. Therefore, to access the survival/anti-disease role of the circadian system at the entire body level, we would have to investigate the stress response using the disease models of animals.


  1. 1.

    Reppert SM, Weaver DR (2002) Coordination of circadian timing in mammals. Nature 418:935–941

  2. 2.

    Doherty CJ, Kay SA (2010) Circadian control of global gene expression patterns. Annu Rev Genet 44:419–444

  3. 3.

    Ikeda M, Nomura M (1997) cDNA cloning and tissue-specific expression of a novel basic helix-loop-helix/PAS protein (BMAL1) and identification of alternatively spliced variants with alternative translation initiation site usage. Biochem Biophys Res Commun 233:258–264

  4. 4.

    Bunger MK, Wilsbacher LD, Moran SM, Cledenin C, Radcriffe LA, Hogenesch JB, Simon MC, Takahashi JS, Bradfield CA (2000) Mop3 is an essential component of the master circadian pacemaker in mammals. Cell 103:1009–1017

  5. 5.

    van der Horst GT, Muijtjens M, Kobayashi K, Takano R, Kanno S, Takao M, de Wit J, Verkerk A, Eker AP, van Leenen D, Buijs R, Bootsma D, Hoeijmakers JH, Yasui A (1999) Mammalian Cry1 and Cry2 are essential for maintenance of circadian rhythms. Nature 398:627–630

  6. 6.

    Crane BR, Young MW (2014) Interactive features of proteins composing eukaryotic circadian clocks. Annu Rev Biochem 83:191–219

  7. 7.

    Mehra A, Baker CL, Loros JJ, Dunlap JC (2009) Post-translational modifications in circadian rhythms. Trends Biochem Sci 34:483–490

  8. 8.

    Tamaru T, Okada M, Nagai K, Nakagawa H, Takamatsu K (1999) Periodically fluctuating protein kinases phosphorylate CLOCK, the putative target in the suprachiasmatic nucleus. J Neurochem 72:2191–2197

  9. 9.

    Lee C, Etchegaray JP, Cagampang FR, Loudon AS, Reppert SM (2001) Posttranslational mechanisms regulate the mammalian circadian clock. Cell 107:855–867

  10. 10.

    Tamaru T, Isojima Y, van der Horst GT, Takei K, Nagai K, Takamatsu K (2003) Nucleocytoplasmic shuttling and phosphorylation of BMAL1 are regulated by circadian clock in cultured fibroblasts. Genes Cells 8:973–983

  11. 11.

    Kloss B, Price JL, Saez L, Blau J, Rothenfluh A, Wesley CS, Young MW (2005) The Drosophila clock gene double-time encodes a protein closely related to human casein kinase Iepsilon. Cell 94:97–107

  12. 12.

    Tamaru T, Hirayama J, Isojima Y, Nagai K, Norioka S, Takamatsu K, Sassone-Corsi P (2009) CK2alpha phosphorylates BMAL1 to regulate the mammalian clock. Nat Struct Mol Biol 16:446–448

  13. 13.

    Tamaru T, Hattori M, Honda K, Nakahata Y, Sassone-Corsi P, van der Horst GT, Ozawa T, Takamatsu K (2015) CRY drives cyclic CK2-mediated BMAL1 phosphorylation to control the mammalian circadian clock. PLoS Biol 13(11):e1002293

  14. 14.

    Hirayama J, Sahar S, Grimaldi B, Tamaru T, Takamatsu K, Nakahata Y, Sassone-Corsi P (2007) CLOCK-mediated acetylation of BMAL1 controls circadian function. Nature 450:1086–1090

  15. 15.

    Nakahata Y, Kaluzova M, Grimaldi B, Sahar S, Hirayama J, Chen D, Guarente LP, Sassone-Corsi P (2008) The NAD + -dependent deacetylase SIRT1 modulates CLOCK-mediated chromatin remodeling and circadian control. Cell 25:329–340

  16. 16.

    Tamaru T, Hattori M, Honda K, Benjamin I, Ozawa T, Takamatsu K (2011) Synchronization of circadian Per2 rhythms and HSF1-BMAL1:CLOCK interaction in mouse fibroblasts after short-term heat shock pulse. PLoS One 6:e24521

  17. 17.

    Ohnishi N, Tahara Y, Kuriki D, Haraguchi A, Shibata S (2014) Warm water bath stimulates phase-shifts of the peripheral circadian clocks in PER2:LUCIFERASE mouse. PLoS One 9:e100272

  18. 18.

    Tamaru T, Hattori M, Ninomiya Y, Kawamura G, Varès G, Honda K, Mishra D-P, Wang B, Benjamin I, Sassone-Corsi P, Ozawa T, Takamatsu K (2013) ROS stress resets circadian clocks to coordinate pro-survival signals. PLoS One 8:e82006

  19. 19.

    Kon N, Hirota T, Kawamoto T, Kato Y, Tsubota T, Fukada Y, Lee SK, Achieng E, Maddox C, Chen SC, Iuvone PM, Fukuhara C (2008) Activation of TGF-beta/activin signalling resets the circadian clock through rapid induction of Dec1 transcripts. Nat Cell Biol 10:1463–1469

  20. 20.

    Lee SK, Achieng E, Maddox C, Chen SC, Iuvone PM, Fukuhara C (2011) Extracellular low pH affects circadian rhythm expression in human primary fibroblasts. Biochem Biophys Res Commun 416:337–342

  21. 21.

    Mortola JP, Seifert EL (2000) Hypoxic depression of circadian rhythms in adult rats. J Appl Physiol 88:365–368

  22. 22.

    Fenelon K, Seifert EL, Mortola JP (2000) Hypoxic depression of circadian oscillations in sino-aortic denervated rats. Respir Physiol 122:61–69

  23. 23.

    Okabe T, Kumagai M, Nakajima Y, Shirotake S, Kodaira K, Oyama M, Ueno M, Masaaki I (2014) The impact of HIF1alpha on the Per2 circadian rhythm in renal cancer cell lines. PLoS One 9:e109693

  24. 24.

    van Oosterhout F, Fisher SP, van Diepen HC, Watson TS, Houben T, VanderLeest HT, Thompson S, Peirson SN, Foster RG, Meijer JH (2012) Ultraviolet light provides a major input to non-image-forming light detection in mice. Curr Biol 22:1397–1402

  25. 25.

    Schieber M, Chandel NS (2014) ROS function in redox signaling and oxidative stress. Curr Biol 24:R453–R462

  26. 26.

    Anckar J, Sistonen L (2011) Regulation of HSF1 function in the heat stress response: implications in aging and disease. Annu Rev Biochem 80:1089–1115

  27. 27.

    Shah P, He YY (2015) Molecular regulation of UV-induced DNA repair. Photochem Photobiol 91:254–264

  28. 28.

    Kato T Jr, Delhase M, Hoffmann A, Karin M (2003) CK2 is a C-terminal IkappaB kinase responsible for NF-kappaB activation during the UV response. Mol Cell 12:829–839

  29. 29.

    Apopa PL, He X, Ma Q, Hirotsu Y, Katsuoka F et al (2008) Phosphorylation of Nrf2 in the transcription activation domain by casein kinase 2 (CK2) is critical for the nuclear translocation and transcription activation function of Nrf2 in IMR-32 neuroblastoma cells. J Biochem Mol Toxicol 22:63–76

  30. 30.

    Hybertson BM, Gao B (2014) Role of the Nrf2 signaling system in health and disease. Clin Genet 86:447–452

  31. 31.

    McIntosh BE, Hogenesch JB, Bradfield CA (2010) Mammalian Per-Arnt-Sim proteins in environmental adaptation. Annu Rev Physiol 72:625–645

  32. 32.

    Goldsmith CS, Bell-Pedersen D (2013) Diverse roles for MAPK signaling in circadian clocks. Adv Genet 84:1–39

  33. 33.

    Patel SA, Velingkaar NS, Kondratov RV (2014) Transcriptional control of antioxidant defense by the circadian clock. Antioxid Redox Signal 20:2997–3006

  34. 34.

    Kinmonth-Schultz HA, Golembeski GS, Imaizumi T (2013) Circadian clock-regulated physiological outputs: dynamic responses in nature. Semin Cell Dev Biol 24:407–413

  35. 35.

    Weindling E, Bar-Nun S (2015) Sir2 links the unfolded protein response and the heat shock response in a stress response network. Biochem Biophys Res Commun 457:473–478

  36. 36.

    Raychaudhuri S, Loew C, Körner R, Pinkert S, Theis M, Hayer-Hartl M, Buchholz F, Hartl FU (2014) Interplay of acetyltransferase EP300 and the proteasome system in regulating heat shock transcription factor 1. Cell 156:975–985

  37. 37.

    Westerheide SD, Anckar J, Stevens SM Jr, Sistonen L, Morimoto RI (2009) Stress-inducible regulation of heat shock factor 1 by the deacetylase SIRT1. Science 323:1063–1066

  38. 38.

    Pekovic-Vaughan V, Gibbs J, Yoshitane H, Yang N, Pathiranage D, Guo B, Sagami A, Taguchi K, Bechtold D, Loudon A, Yamamoto M, Chan J, van der Horst GT, Fukada Y, Meng QJ (2014) The circadian clock regulates rhythmic activation of the NRF2/glutathione-mediated antioxidant defense pathway to modulate pulmonary fibrosis. Genes Dev 28:548–560

  39. 39.

    Spengler ML, Kuropatwinski KK, Comas M, Gasparian AV, Fedtsova N et al (2012) Core circadian protein CLOCK is a positive regulator of NF-κB-mediated transcription. Proc Natl Acad Sci USA 109:E2457–E2465

  40. 40.

    Logan IR, McNeill HV, Cook S, Lu X, Meek DW, Fuller-Pace FV, Lunec J, Robson CN (2009) Heat shock factor-1 modulates p53 activity in the transcriptional response to DNA damage. Nucleic Acids Res 37:2962–2973

  41. 41.

    Li Q, Martinez JD (2011) P53 is transported into the nucleus via an Hsf1-dependent nuclear localization mechanism. Mol Carcinog 50:143–152

  42. 42.

    Miki T, Matsumoto T, Zhao Z, Lee CC (2013) p53 regulates Period2 expression and the circadian clock. Nat Commun 4:2444

Download references

Author information

Correspondence to Teruya Tamaru.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Tamaru, T., Ikeda, M. Circadian adaptation to cell injury stresses: a crucial interplay of BMAL1 and HSF1. J Physiol Sci 66, 303–306 (2016).

Download citation


  • Circadian clock
  • Heat shock
  • Oxidative stress
  • Adaptation
  • Protein kinase