NPAS2: an analog of clock operative in the mammalian forebrain.
Neuronal PAS domain protein 2 (NPAS2) is a transcription factor expressed primarily in the mammalian forebrain. NPAS2 is highly related in primary amino acid sequence to Clock, a transcription factor expressed in the suprachiasmatic nucleus that heterodimerizes with BMAL1 and regulates circadian rhythm. To investigate the biological role of NPAS2, we prepared a neuroblastoma cell line capable of conditional induction of the NPAS2:BMAL1 heterodimer and identified putative target genes by representational difference analysis, DNA microarrays, and Northern blotting. Coinduction of NPAS2 and BMAL1 activated transcription of the endogenous Per1, Per2, and Cry1 genes, which encode negatively activating components of the circadian regulatory apparatus, and repressed transcription of the endogenous BMAL1 gene. Analysis of the frontal cortex of wild-type mice kept in a 24-hour light-dark cycle revealed that Per1, Per2, and Cry1 mRNA levels were elevated during darkness and reduced during light, whereas BMAL1 mRNA displayed the opposite pattern. In situ hybridization assays of mice kept in constant darkness revealed that Per2 mRNA abundance did not oscillate as a function of the circadian cycle in NPAS2-deficient mice. Thus, NPAS2 likely functions as part of a molecular clock operative in the mammalian forebrain.
Reick
M
M
Department of Biochemistry, Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
Garcia
J A
JA
Dudley
C
C
McKnight
S L
SL
D056930:ARNTL Transcription Factors; D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D001683:Biological Clocks / Q000502:physiology*; D015152:Blotting, Northern; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D002460:Cell Line; D002940:Circadian Rhythm / Q000502:physiology*; D003001:Cloning, Molecular; D056931:Cryptochromes; D003624:Darkness; D019281:Dimerization; D029721:Drosophila Proteins; D004441:Ecdysterone / Q000031:analogs & derivatives* / Q000494:pharmacology; D005136:Eye Proteins; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D017403:In Situ Hybridization; D008027:Light; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D056950:Period Circadian Proteins; D017956:Photoreceptor Cells, Invertebrate; D016548:Prosencephalon / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D056931:Cryptochromes; D029721:Drosophila Proteins; D004441:Ecdysterone; D005136:Eye Proteins; D005420:Flavoproteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D043562:Receptors, G-Protein-Coupled; D015534:Trans-Activators; D014157:Transcription Factors; C538960:BMAL1 protein, human; C538961:Bmal1 protein, mouse; C538963:CRY1 protein, human; C538964:Cry1 protein, mouse; C104264:NPAS2 protein, human; C491259:Npas2 protein, mouse; C539022:PER1 protein, human; C421902:PER2 protein, human; C539023:Per1 protein, mouse; C513312:Per2 protein, mouse; C119828:cry protein, Drosophila; C008999:ponasterone A; C538943:CLOCK protein, human; C538944:Clock protein, mouse