WC-2 mediates WC-1-FRQ interaction within the PAS protein-linked circadian feedback loop of Neurospora.
Eukaryotic circadian clocks comprise feedback loops where PAS domain-containing transcriptional activators drive gene expression of negative elements. In NEUROSPORA:, clock models posit a White Collar complex (WCC) containing WC-1 and WC-2 that activates expression of the central clock gene frequency (frq); FRQ protein is hypothesized to feed back to block the activity of the WCC. We have characterized the WC-2 protein and its role in this complex: WC-2 is an abundant constitutive nuclear protein, in contrast to rhythmically expressed FRQ and WC-1. WC-2 interacts with WC-1 and FRQ but, significantly, WC-1 and FRQ do not interact in the absence of WC-2. By quantifying the relative numbers of WC-2, FRQ and WC-1 proteins and complexes in cell extracts, both the numbers and types of complexes at different circadian times were estimated, yielding results consistent with the model. Constitutive and abundant WC-2 appears to provide a scaffold allowing for the interaction of two limiting and rhythmically out-of-phase proteins, FRQ and WC-1, and this temporal and physical relationship may be responsible for rhythmic expression of frq.
Departments of Biochemistry and Genetics, Dartmouth Medical School, Hanover, NH 03755, USA.
D L
DL
Denault
J J
JJ
Loros
J C
JC
Dunlap
D001683:Biological Clocks; D002940:Circadian Rhythm / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D005246:Feedback; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D009491:Neurospora / Q000235:genetics / Q000502:physiology*; D014176:Protein Biosynthesis; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; C087405:FRQ protein, Neurospora crassa; D005656:Fungal Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; C105589:wc-1 protein, Neurospora crassa; C103772:white collar 2 protein, Neurospora