title: Cryptochrome, circadian cycle, cell cycle checkpoints, and cancer.
abstract: It has been reported that disruption of the circadian clock may lead to increased risk of breast cancer in humans and to a high rate or ionizing radiation-induced tumors and mortality in mice. Cryptochrome 1 and cryptochrome 2 proteins are core components of the mammalian circadian clock and mice mutated in both genes are arrhythmic. We tested Cry1-/- Cry2-/- mice and fibroblasts derived from these mice for radiation-induced cancer and killing and DNA damage checkpoints and killing, respectively. We find that the mutant mice are indistinguishable from the wild-type controls with respect to radiation-induced morbidity and mortality. Similarly, the Cry1-/- Cry2-/-mutant fibroblasts are indistinguishable from the wild-type controls with respect to their sensitivity to ionizing radiation and UV radiation and ionizing radiation-induced DNA damage checkpoint response. Our data suggest that disruption of the circadian clock in itself does not compromise mammalian DNA repair and DNA damage checkpoints and does not predispose mice to spontaneous and ionizing radiation-induced cancers. We conclude that the effect of circadian clock disruption on cellular response to DNA damage and cancer predisposition in mice may depend on the mechanism by which the clock is disrupted.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.
authors.forename: Michele A
authors.initials: MA
authors.lastname: Gauger
authors.forename: Aziz
authors.initials: A
authors.lastname: Sancar
mesh_terms: D056930:ARNTL Transcription Factors; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D056931:Cryptochromes; D004249:DNA Damage; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000528:radiation effects; D005420:Flavoproteins / Q000235:genetics / Q000502:physiology*; D007178:Inbreeding; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009369:Neoplasms / Q000473:pathology*; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis; D014157:Transcription Factors / Q000096:biosynthesis
chemical_list: D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056931:Cryptochromes; D005420:Flavoproteins; D016271:Proto-Oncogene Proteins c-myc; D014157:Transcription Factors; C538960:BMAL1 protein, human; C538961:Bmal1 protein, mouse; C538963:CRY1 protein, human; C538966:CRY2 protein, human; C538964:Cry1 protein, mouse; C538967:Cry2 protein, mouse; C489428:Myc protein, mouse