Drosophila CLOCK target gene characterization: implications for circadian tissue-specific gene expression

CLK binding occurs at at least 800 sites with peak activity in the early night.

• The CLK partner protein CYCLE is present at most CLK binding sites.
• PER, a transcriptional repressor, joins the CLK/CYC complex 4-6 hours later.
• Approximately 30% of target genes exhibit cycles of RNA polymerase II binding.
• Many genes produce cycling RNAs that were not previously identified in RNA cycling studies.
• Different RNA isoforms and tissue heterogeneity may contribute to observed cycling.
• CLK targets vary across tissues, suggesting distinct regulatory mechanisms at play.

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