GSE127192
MYC-associated factor X, MAX, binds BMAL1 targeted genomic regions with high affinity [ChIP-Seq]
Purpose: quantitavive RT-PCR and ChIP analyses suggested that the MYC-Associated factor X, MAX, and the essential circadian regulator, BMAL1, might be recruited on the same E-box containing regulatory regions within the promoters of clock target genes. To explore this possibility, we performed ChIP-seq experiments in human cancer MDA-MB-231 cells. Methods: Chromatin samples from human cancer MDA-MB-231 cells were immunoprecipitated with specific antibodies against BMAL1 and MAX proteins. Immunoprecipitated DNA was sequenced using Illumina HiSeq 2000 sequencer. Results: ChIP-seq analysis revealed a large number of genomic regions bound by MAX (around 13000 peaks), while BMAL1 binding was limited to about 800 regions. BMAl1 and MAX bound regions comprised both promoters and distal sites. Coherently with the circadian role of BMAL1 and its preference for E-box-containing sites, ontological annotation of BMAL1 bound regions showed a significant enrichment for circadian regulated genes and E-box motifs. The 85% of the BMAL bound sites overlapped with MAX bound regions. MAX enrichment was higher on the genomic regions co-bound by BMAL1 compared with MAX binding loci sites in which BMAL1 was not present, thus indicating that MAX/BMAL1 sites are bound by MAX with high affinity. Strikingly, MAX enrichment was observed on all E-box-containing promoters of the clock core genes. Overall design: Chromatin samples from human cancer MDA-MB-231 cells were immunoprecipitated with specific antibodies against BMAL1 and MAX proteins. Immunoprecipitated DNA was sequenced using Illumina HiSeq 2000 sequencer.