ChIP-seq H4 and AcH4 in WT and del.ncu09482

Post-translational modifications (PTMs) on histones have been found to play diverse functions in regulating chromatin events and gene expression. The operation of circadian clocks heavily relies on finely tuned and timely expression of the proteins comprising core oscillators. However, most studies of PTMs’ effects on circadian clocks have been conducted using static systems in which circadian clocks are rendered arrhythmic due to the essential role of PTMs on gene expression. In the Neurospora circadian system, the White Collar Complex (WCC), a heterodimeric transcription factor formed from White Collar-1 (WC-1) and White Collar-2 (WC-2), serves the function of the BMAL1/CLOCK heterodimer in mammals, driving expression of circadian negative arm component(s), a principal one in Neurospora encoded by the gene frequency (frq). FRQ interacts with FRH (FRQ-interacting helicase) and CK-1 forming a stable complex that represses its own expression by inhibiting WCC. In this study, a genetic screen identified a gene, designated as brd-8, that encodes a conserved auxiliary subunit of the NuA4 histone acetylation complex. Loss of brd-8 reduces H4 acetylation and RNA polymerase (Pol) II occupancy at frq and other known circadian genes, and leads to a long circadian period, delayed phase, and defective overt circadian output at some temperatures. In addition to strongly associating with the NuA4 histone acetyltransferase complex, BRD-8 is also found complexed with the transcription elongation regulator BYE-1. Expression of brd-8, bye-1, histone hH2Az, and several NuA4 subunits is controlled by the circadian clock, indicating that the molecular clock both regulates the basic chromatin status and is regulated by changes in chromatin. Taken together, our data identify new auxiliary elements of the fungal NuA4 complex having homology to mammalian components, which along with conventional NuA4 subunits, are required for timely and dynamic frq expression and thereby a normal and persistent circadian rhythm. ChIP-seq histone H4 and acetylated histone H4 in WT at D20 (cultured by shaking in the dark for 20 hrs) and del.ncu09482 at D24 (cultured by shaking in the dark for 26 hrs)