Drosophila CRYPTOCHROME Is a Circadian Transcriptional Repressor

Drosophila CRY functions as a transcriptional repressor that is essential for the oscillation of peripheral circadian clocks.

• In cry(b) mutant eyes, RNA levels of genes activated by CLOCK and CYCLE are derepressed.
• Overexpression of CRY and PERIOD represses CLK/CYC activity, but neither protein represses individually.
• Repression by CRY is limited to peripheral clocks, as it does not significantly affect pacemaker neurons.
• Removing two repressors, PER and CRY, increases CLK/CYC activity and leads to ectopic expression of the timeless clock gene.

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