Circadian clock-specific roles for the light response protein WHITE COLLAR-2.
To understand the role of white collar-2 in the Neurospora circadian clock, we examined alleles of wc-2 thought to encode partially functional proteins. We found that wc-2 allele ER24 contained a conservative mutation in the zinc finger. This mutation results in reduced levels of circadian rhythm-critical clock gene products, frq mRNA and FRQ protein, and in a lengthened period of the circadian clock. In addition, this mutation altered a second canonical property of the clock, temperature compensation: as temperature increased, period length decreased substantially. This temperature compensation defect correlated with a temperature-dependent increase in overall FRQ protein levels, with the relative increase being greater in wc-2 (ER24) than in wild type, while overall frq mRNA levels were largely unaltered by temperature. We suggest that this temperature-dependent increase in FRQ levels partially rescues the lowered levels of FRQ resulting from the wc-2 (ER24) defect, yielding a shorter period at higher temperatures. Thus, normal activity of the essential clock component WC-2, a positive regulator of frq, is critical for establishing period length and temperature compensation in this circadian system.
Collett
M A
MA
Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Dunlap
J C
JC
Loros
J J
JJ
D000595:Amino Acid Sequence; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008027:Light; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000235:genetics* / Q000378:metabolism* / Q000528:radiation effects; D012326:RNA Splicing; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; C087405:FRQ protein, Neurospora crassa; D005656:Fungal Proteins; D012331:RNA, Fungal; D012333:RNA, Messenger; D014157:Transcription Factors; C103772:white collar 2 protein, Neurospora