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

Area of Science:

• Chronobiology
• Molecular Biology
• Genetics

Background:

• The circadian clock regulates daily biological rhythms.
• CLOCK (CLK) is a key transcriptional regulator in Drosophila's circadian clock.
• Understanding CLK's direct targets is crucial for deciphering circadian transcriptional regulation.

Purpose of the Study:

• To identify direct target genes of CLOCK (CLK).
• To investigate circadian transcriptional regulation mechanisms in Drosophila.
• To characterize CLK binding patterns and associated regulatory proteins.

Main Methods:

• Chromatin immunoprecipitation (ChIP) tiling array assays (ChIP-chip) were performed.
• Circadian proteins, including CLK, CYCLE (CYC), and PERIOD (PER), were analyzed.
• RNA polymerase II (Pol II) binding was assessed to identify actively transcribed genes.

Main Results:

• CLK binding was observed at over 800 genomic sites, peaking in the early night.
• The CLK/CYC heterodimer binds most CLK target sites, followed by PER.
• Approximately 30% of CLK targets showed cycling Pol II binding, with some generating novel cycling RNAs.
• Tissue-specific CLK targets suggest complex regulatory mechanisms involving partner proteins.

Conclusions:

• CLK directly regulates a substantial number of genes in Drosophila, with conserved regulation similar to core clock genes.
• Novel cycling RNAs were identified, highlighting the complexity of circadian gene expression and potential tissue heterogeneity.
• Tissue-specific regulation by CLK implies the involvement of additional factors and mechanisms in controlling gene expression patterns.