mCRY1 and mCRY2 are essential components of the negative limb of the circadian clock feedback loop.
We determined that two mouse cryptochrome genes, mCry1 and mCry2, act in the negative limb of the clock feedback loop. In cell lines, mPER proteins (alone or in combination) have modest effects on their cellular location and ability to inhibit CLOCK:BMAL1 -mediated transcription. This suggested cryptochrome involvement in the negative limb of the feedback loop. Indeed, mCry1 and mCry2 RNA levels are reduced in the central and peripheral clocks of Clock/Clock mutant mice. mCRY1 and mCRY2 are nuclear proteins that interact with each of the mPER proteins, translocate each mPER protein from cytoplasm to nucleus, and are rhythmically expressed in the suprachiasmatic circadian clock. Luciferase reporter gene assays show that mCRY1 or mCRY2 alone abrogates CLOCK:BMAL1-E box-mediated transcription. The mPER and mCRY proteins appear to inhibit the transcriptional complex differentially.
Kume
K
K
Laboratory of Developmental Chronobiology, Pediatric Service, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
Zylka
M J
MJ
Sriram
S
S
Shearman
L P
LP
Weaver
D R
DR
Jin
X
X
Maywood
E S
ES
Hastings
M H
MH
Reppert
S M
SM
D016475:3T3 Cells; D056930:ARNTL Transcription Factors; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D001683:Biological Clocks / Q000502:physiology*; D015153:Blotting, Western; D056926:CLOCK Proteins; D019556:COS Cells; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005246:Feedback / Q000502:physiology; D005260:Female; D005420:Flavoproteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D056950:Period Circadian Proteins; D017956:Photoreceptor Cells, Invertebrate; D012333:RNA, Messenger / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D013493:Suprachiasmatic Nucleus / Q000737:chemistry / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D015534:Trans-Activators; D014157:Transcription Factors; C538960:BMAL1 protein, human; C538961:Bmal1 protein, mouse; C539022:PER1 protein, human; C421902:PER2 protein, human; C539023:Per1 protein, mouse; C513312:Per2 protein, mouse; C119828:cry protein, Drosophila; C538943:CLOCK protein, human; C538944:Clock protein, mouse