title: The ratio of intracellular CRY proteins determines the clock period length.
abstract: Although a deficiency in CRY1 or CRY2 correlates with a shorter or longer circadian period, the regulation of CRY proteins in the circadian period has not been well studied. In this study, we found that both CRY1 and CRY2 were able to rescue oscillation in CRY null cells and that they displayed different periods. Furthermore, we demonstrated that protein nuclear import rates, not protein stability, regulate the period-length at the cellular level. Co-transfection of CRY1 and CRY2 in various ratios in the same cells gives rise to the predicted period length in a dose-dependent manner. Given the distinct characteristics of the C-terminal tails of the CRY1 and CRY2 proteins, our study addresses a long-standing hypothesis that the ratio of these two CRY molecules affects the clock period.
authors.affiliation: College of Biological Sciences, China Agricultural University, Beijing 100083, China; National Institute of Biological Sciences, Beijing 102206, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.affiliation: National Institute of Biological Sciences, Beijing 102206, China; School of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xiong
authors.affiliation: National Institute of Biological Sciences, Beijing 102206, China. Electronic address: zhangerquan@nibs.ac.cn.
authors.forename: Eric Erquan
authors.initials: EE
authors.lastname: Zhang
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D002467:Cell Nucleus / Q000502:physiology*; D057906:Circadian Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D056931:Cryptochromes / Q000378:metabolism*; D025461:Feedback, Physiological / Q000502:physiology; D005347:Fibroblasts / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans
chemical_list: C538963:CRY1 protein, human; C538966:CRY2 protein, human; D056931:Cryptochromes
keywords: C-terminal tail; Circadian rhythms; Cryptochrome; Nuclear importing rate; Period; Protein stability