Product: Clock Antibody
Catalog: AF0323
Description: Rabbit polyclonal antibody to Clock
Application: WB IHC IF/ICC
Reactivity: Human, Mouse, Rat
Prediction: Pig, Bovine, Horse, Sheep, Rabbit, Dog, Chicken, Xenopus
Mol.Wt.: 95kDa; 95kD(Calculated).
Uniprot: O15516
RRID: AB_2833486

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Product Info

WB 1:500-1:3000, IHC 1:50-1:200, IF/ICC 1:100-1:500
*The optimal dilutions should be determined by the end user.

WB: For western blot detection of denatured protein samples. IHC: For immunohistochemical detection of paraffin sections (IHC-p) or frozen sections (IHC-f) of tissue samples. IF/ICC: For immunofluorescence detection of cell samples. ELISA(peptide): For ELISA detection of antigenic peptide.

Pig(100%), Bovine(100%), Horse(100%), Sheep(100%), Rabbit(100%), Dog(100%), Chicken(100%), Xenopus(91%)
Clock Antibody detects endogenous levels of total Clock.
Cite Format: Affinity Biosciences Cat# AF0323, RRID:AB_2833486.
The antiserum was purified by peptide affinity chromatography using SulfoLink™ Coupling Resin (Thermo Fisher Scientific).
Rabbit IgG in phosphate buffered saline , pH 7.4, 150mM NaCl, 0.02% sodium azide and 50% glycerol. Store at -20 °C. Stable for 12 months from date of receipt.


bHLHe8; Circadian locomoter output cycles kaput protein; Circadian locomoter output cycles protein kaput; Circadian Locomotor Output Cycles Kaput; Circadium Locomotor Output Cycles Kaput; Class E basic helix-loop-helix protein 8; CLOCK; Clock circadian regulator; Clock homolog; Clock protein; CLOCK_HUMAN; hCLOCK; KIAA0334;



Hair follicles (at protein level). Expressed in all tissues examined including spleen, thymus, prostate, testis, ovary, small intestine, colon, leukocytes, heart, brain, placenta, lung, liver, skeletal muscle, kidney and pancreas. Highest levels in testis and skeletal muscle. Low levels in thymus, lung and liver. Expressed in all brain regions with highest levels in cerebellum. Highly expressed in the suprachiasmatic nucleus (SCN).

CLOCK ARNTL/2-CLOCK heterodimers activate E-box element (3'- CACGTG-5') transcription of a number of proteins of the circadian clock. Activates transcription of PER1 and PER2. This transcription is inhibited in a feedback loop by PER and CRY proteins. Has intrinsic histone acetyltransferase activity and this enzymatic function contributes to chromatin-remodeling events implicated in circadian control of gene expression. Acetylates primarily histones H3 and H4.



Score>80(red) has high confidence and is suggested to be used for WB detection. *The prediction model is mainly based on the alignment of immunogen sequences, the results are for reference only, not as the basis of quality assurance.

Model Confidence:
High(score>80) Medium(80>score>50) Low(score<50) No confidence

PTMs - O15516 As Substrate

Site PTM Type Enzyme
K31 Acetylation
K41 Acetylation
S59 Phosphorylation
K67 Sumoylation
K76 Ubiquitination
K85 Ubiquitination
S164 Phosphorylation
S177 Phosphorylation
K186 Ubiquitination
K205 Ubiquitination
Y331 Phosphorylation
K402 Ubiquitination
S403 Phosphorylation
S406 Phosphorylation
S408 Phosphorylation
K418 Ubiquitination
S427 Phosphorylation P49841 (GSK3B)
T429 Phosphorylation
S431 Phosphorylation
S434 Phosphorylation
S437 Phosphorylation
T443 Phosphorylation
S446 Phosphorylation
T451 Phosphorylation Q00535 (CDK5)
T461 Phosphorylation Q00535 (CDK5)
R702 Methylation
S836 Phosphorylation
K842 Sumoylation

Research Backgrounds


Transcriptional activator which forms a core component of the circadian clock. The circadian clock, an internal time-keeping system, regulates various physiological processes through the generation of approximately 24 hour circadian rhythms in gene expression, which are translated into rhythms in metabolism and behavior. It is derived from the Latin roots 'circa' (about) and 'diem' (day) and acts as an important regulator of a wide array of physiological functions including metabolism, sleep, body temperature, blood pressure, endocrine, immune, cardiovascular, and renal function. Consists of two major components: the central clock, residing in the suprachiasmatic nucleus (SCN) of the brain, and the peripheral clocks that are present in nearly every tissue and organ system. Both the central and peripheral clocks can be reset by environmental cues, also known as Zeitgebers (German for 'timegivers'). The predominant Zeitgeber for the central clock is light, which is sensed by retina and signals directly to the SCN. The central clock entrains the peripheral clocks through neuronal and hormonal signals, body temperature and feeding-related cues, aligning all clocks with the external light/dark cycle. Circadian rhythms allow an organism to achieve temporal homeostasis with its environment at the molecular level by regulating gene expression to create a peak of protein expression once every 24 hours to control when a particular physiological process is most active with respect to the solar day. Transcription and translation of core clock components (CLOCK, NPAS2, ARNTL/BMAL1, ARNTL2/BMAL2, PER1, PER2, PER3, CRY1 and CRY2) plays a critical role in rhythm generation, whereas delays imposed by post-translational modifications (PTMs) are important for determining the period (tau) of the rhythms (tau refers to the period of a rhythm and is the length, in time, of one complete cycle). A diurnal rhythm is synchronized with the day/night cycle, while the ultradian and infradian rhythms have a period shorter and longer than 24 hours, respectively. Disruptions in the circadian rhythms contribute to the pathology of cardiovascular diseases, cancer, metabolic syndromes and aging. A transcription/translation feedback loop (TTFL) forms the core of the molecular circadian clock mechanism. Transcription factors, CLOCK or NPAS2 and ARNTL/BMAL1 or ARNTL2/BMAL2, form the positive limb of the feedback loop, act in the form of a heterodimer and activate the transcription of core clock genes and clock-controlled genes (involved in key metabolic processes), harboring E-box elements (5'-CACGTG-3') within their promoters. The core clock genes: PER1/2/3 and CRY1/2 which are transcriptional repressors form the negative limb of the feedback loop and interact with the CLOCK|NPAS2-ARNTL/BMAL1|ARNTL2/BMAL2 heterodimer inhibiting its activity and thereby negatively regulating their own expression. This heterodimer also activates nuclear receptors NR1D1/2 and RORA/B/G, which form a second feedback loop and which activate and repress ARNTL/BMAL1 transcription, respectively. Regulates the circadian expression of ICAM1, VCAM1, CCL2, THPO and MPL and also acts as an enhancer of the transactivation potential of NF-kappaB. Plays an important role in the homeostatic regulation of sleep. The CLOCK-ARNTL/BMAL1 heterodimer regulates the circadian expression of SERPINE1/PAI1, VWF, B3, CCRN4L/NOC, NAMPT, DBP, MYOD1, PPARGC1A, PPARGC1B, SIRT1, GYS2, F7, NGFR, GNRHR, BHLHE40/DEC1, ATF4, MTA1, KLF10 and also genes implicated in glucose and lipid metabolism. Promotes rhythmic chromatin opening, regulating the DNA accessibility of other transcription factors. The CLOCK-ARNTL2/BMAL2 heterodimer activates the transcription of SERPINE1/PAI1 and BHLHE40/DEC1. The preferred binding motif for the CLOCK-ARNTL/BMAL1 heterodimer is 5'-CACGTGA-3', which contains a flanking Ala residue in addition to the canonical 6-nucleotide E-box sequence. CLOCK specifically binds to the half-site 5'-CAC-3', while ARNTL binds to the half-site 5'-GTGA-3'. The CLOCK-ARNTL/BMAL1 heterodimer also recognizes the non-canonical E-box motifs 5'-AACGTGA-3' and 5'-CATGTGA-3'. CLOCK has an intrinsic acetyltransferase activity, which enables circadian chromatin remodeling by acetylating histones and nonhistone proteins, including its own partner ARNTL/BMAL1. Represses glucocorticoid receptor NR3C1/GR-induced transcriptional activity by reducing the association of NR3C1/GR to glucocorticoid response elements (GREs) via the acetylation of multiple lysine residues located in its hinge region. The acetyltransferase activity of CLOCK is as important as its transcription activity in circadian control. Acetylates metabolic enzymes IMPDH2 and NDUFA9 in a circadian manner. Facilitated by BMAL1, rhythmically interacts and acetylates argininosuccinate synthase 1 (ASS1) leading to enzymatic inhibition of ASS1 as well as the circadian oscillation of arginine biosynthesis and subsequent ureagenesis. Drives the circadian rhythm of blood pressure through transcriptional activation of ATP1B1 (By similarity).


Ubiquitinated, leading to its proteasomal degradation.

O-glycosylated; contains O-GlcNAc. O-glycosylation by OGT prevents protein degradation by inhibiting ubiquitination. It also stabilizes the CLOCK-ARNTL/BMAL1 heterodimer thereby increasing CLOCK-ARNTL/BMAL1-mediated transcriptional activation of PER1/2/3 and CRY1/2.

Phosphorylation is dependent on the CLOCK-ARNTL/BMAL1 heterodimer formation. Phosphorylation enhances the transcriptional activity, alters the subcellular localization and decreases the stability of the heterodimer by promoting its degradation. Phosphorylation shows circadian variations in the liver. May be phosphorylated by CSNK1D and CKSN1E.

Sumoylation enhances its transcriptional activity and interaction with ESR1, resulting in up-regulation of ESR1 activity. Estrogen stimulates sumoylation. Desumoylation by SENP1 negatively regulates its transcriptional activity. Sumoylation stimulates cell proliferation and increases the proportion of S phase cells in breast cancer cell lines.

Undergoes lysosome-mediated degradation in a time-dependent manner in the liver.

Subcellular Location:

Nucleus. Cytoplasm. Cytoplasm>Cytosol.
Note: Shuffling between the cytoplasm and the nucleus is under circadian regulation and is ARNTL/BMAL1-dependent. Phosphorylated form located in the nucleus while the nonphosphorylated form found only in the cytoplasm. Sequestered to the cytoplasm in the presence of ID2 (By similarity). Localizes to sites of DNA damage in a H2AX-independent manner.

Extracellular region or secreted Cytosol Plasma membrane Cytoskeleton Lysosome Endosome Peroxisome ER Golgi apparatus Nucleus Mitochondrion Manual annotation Automatic computational assertionSubcellular location
Tissue Specificity:

Hair follicles (at protein level). Expressed in all tissues examined including spleen, thymus, prostate, testis, ovary, small intestine, colon, leukocytes, heart, brain, placenta, lung, liver, skeletal muscle, kidney and pancreas. Highest levels in testis and skeletal muscle. Low levels in thymus, lung and liver. Expressed in all brain regions with highest levels in cerebellum. Highly expressed in the suprachiasmatic nucleus (SCN).

Subunit Structure:

Component of the circadian clock oscillator which includes the CRY proteins, CLOCK or NPAS2, ARNTL/BMAL1 or ARNTL2/BMAL2, CSNK1D and/or CSNK1E, TIMELESS and the PER proteins (By similarity). Interacts with KMT2A; in a circadian manner (By similarity). Forms a heterodimer with ARNTL/BMAL1. The CLOCK-ARNTL/BMAL1 heterodimer is required for E-box-dependent transactivation, for CLOCK nuclear translocation and degradation, and for phosphorylation of both CLOCK and ARNTL/BMAL1 (By similarity). Interacts with NR3C1 in a ligand-dependent fashion. Interacts with ESR1 and estrogen stimulates this interaction. Interacts with the complex p35/CDK5. Interacts with RELA/p65 (By similarity). Interacts with KAT2B, CREBBP, EP300. Interacts with ID1 and ID3 (By similarity). Interacts with ID2. Interacts with MTA1 (By similarity). Interacts with OGA (By similarity). Interacts with SIRT1 (By similarity). Interacts with CIPC (By similarity). Interacts with EZH2 (By similarity). Interacts with EIF4E, PIWIL1 and DDX4 (By similarity). Interacts with PER2 and CRY1 and the interaction with PER and CRY proteins requires translocation to the nucleus. Interacts with PER1 and CRY2 (By similarity). Interaction of the CLOCK-ARNTL/BMAL1 heterodimer with PER or CRY inhibits transcription activation. Interaction of the CLOCK-ARNTL/BMAL1 with CRY1 is independent of DNA but with PER2 is off DNA. The CLOCK-ARNTL/BMAL1 heterodimer interacts with GSK3B. Interacts with KDM5A. Interacts with MYBBP1A (By similarity). Interacts with THRAP3 (By similarity). Interacts with MED1; this interaction requires the presence of THRAP3 (By similarity). Interacts with NCOA2 (By similarity). The CLOCK-ARNTL/BMAL1 heterodimer interacts with PASD1. Interacts with ASS1 and IMPDH2; in a circadian manner. Interacts with NDUFA9. Interacts with PIWIL2 (via PIWI domain). Interacts with HNF4A.

Research Fields

· Human Diseases > Infectious diseases: Viral > Herpes simplex infection.

· Organismal Systems > Environmental adaptation > Circadian rhythm.   (View pathway)

· Organismal Systems > Nervous system > Dopaminergic synapse.


1). Gao ZR et al. A comprehensive analysis of the circRNA–miRNA–mRNA network in osteocyte-like cell associated with Mycobacterium leprae infection. PLoS Neglected Tropical Diseases 2022 May 2;16(5):e0010379. (PubMed: 35500036) [IF=3.8]

Application: WB    Species: Mice    Sample: BMSCs

Fig 4. Bioinformatics analysis of the gene pathways that were enriched in the N.g MDP–treated osteocytes and verification in vitro. (A and B) Pathway enrichment analysis showed that the differentially expressed genes, including clock and Rora, were associated with Circadian rhythm pathways. The size of the nodes and the intensity of the color indicate the gene number and mean P value. (C) qRT-PCR showed decreased expression of clock mRNA, n = 3. (D) Western blots showed decreased expression of CLOCK, RUNX2, and BGLAP. (E) Quantitative analysis of the expression of CLOCK protein. n = 3. (F) qRT-PCR showed increased expression of clock mRNA after osteogenic induction. (G) In vivo, immunohistochemistry showed increased CLOCK expression in bone mesenchymal stem cells (BMSCs) and osteoblasts, but decreased expression in osteocytes. Scale bar = 10 μm. (H and I) Quantitative analysis of immunohistochemical score of (G). Green arrow, BMSCs; blue arrow, osteoblast; red arrow, osteocyte; Control, the sample was treated with culture medium in vitro or saline only in vivo; MDP, the sample was treated with 1 μg/ml N.g MDP for 36 h in vitro or 2 μg N.g MDP dissolved in 100 μl of saline solution for 10 days in vivo.

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