AJP - Regulatory, Integrative and Comparative Physiology, Vol 241, Issue 1 31-R35, Copyright © 1981 by American Physiological Society
Cycloheximide-induced phase shifting of circadian clock of Neurospora
H. Nakashima, J. Perlman and J. F. Feldman
Cycloheximide (CHX), an inhibitor of cytosolic (80S) protein synthesis in
eucaryotes, causes phase shifts of the circadian clock of Neurospora crassa
when administered as 4-h pulses to cultures in liquid medium. Differential
effects of the pulses at different phases of the circadian cycle were
observed and plotted as a phase-response curve (PRC). Nearly all phase
shifts observed were phase advances, with maximum sensitivity in the middle
of the subjective day. Inhibition of protein synthesis by CHX was the same
at both phases of the cycle. The PRC was the same at 20 and 25 degrees C.
Dose-response curves for the effects of CHX on phase shifting and
inhibition of protein synthesis were determined and showed a striking
parallel in the responses of these two phenomena to CHX. These results
support the view that synthesis of one or more proteins at specific phases
of the circadian cycle is necessary for the normal operation of the
circadian clock of Neurospora.
