Abstract: The invention relates to modulation of circadian rhythm and underlying biological processes.

Abstract: The molecular reaction mechanism that associates the clock gene with stress is elucidated based on the finding that stress is accompanied by an increase in the expression level of Per1 gene in peripheral tissues, stress response does not change the circadian rhythm in peripheral tissues, and Per1 gene increases in its expression level dependently on the responsive element of glucocorticoid existing in its promoter region. This finding is used for stress evaluation. That is, stress can be evaluated for its presence or absence or degree by detection and determination of an increase in the transcript (mRNA) of Per1 gene in peripheral tissues (an increase in the protein coded by Per1 gene).

Abstract: A circadian rhythm control gee cluster (Bmal1 gene, Npas2 gene, Rev-erb?, Dbp gene, Per3 gene, Per2 gene and Per1 gene) having a given expression timing and expression sequence under normal conditions is provided along with a DNA chip having, at least, the circadian control gene group sequentially arranged. There are also provided a method for predicting modulation in expression timing of the circadian rhythm control gene cluster, a method for detecting a circadian rhythm modulation, a method for selecting a circadian rhythm regulator, a method for screening a circadian rhythm regulator, and screening of a substance involving modulation of a circadian rhythm as a side effect, each using the DNA chip.