In theNeurosporacircadian system, the White Collar Complex (WCC) drives expression of the principal circadian negative arm componentfrequency(frq). FRQ interacts with FRH (FRQ-interacting RNA helicase) and CKI, forming a stable complex that represses its own expression by inhibiting WCC. In this study, a genetic screen identified a gene, designated asbrd-8, that encodes a conserved auxiliary subunit of the NuA4 histone acetylation complex. Loss ofbrd-8reduces H4 acetylation and RNA polymerase (Pol) II occupancy atfrqand 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 ofbrd-8, bye-1, histone h2a.z, 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 auxiliary elements of the fungal NuA4 complex having homology to mammalian components, which along with conventional NuA4 subunits, are required for timely and dynamicfrqexpression and thereby a normal and persistent circadian rhythm.