A Positive Role for PERIOD in Mammalian Circadian Gene Expression

PER inhibits CRY-mediated transcriptional repression, suggesting a dual role in circadian regulation.

• PER interferes with the recruitment of CRY into the BMAL1-CLOCK complex.
• This action of PER may enhance transcriptional activity during certain circadian phases.
• Evidence from genetic analyses of Per-deficient or mutant mice supports these findings.
• PER appears to have different roles at various times in the circadian cycle.
• The findings suggest that PER's buffering effect on CRY could extend the duration of rhythmic gene expression.
• Further studies are needed to explore the specific roles of PER at different promoters and circadian phases.

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