CLOCK protein expression summary - The Human Protein Atlas

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CLOCK

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CLOCK

CLOCK INFORMATION
Proteinⁱ Full gene name according to HGNC.	Clock circadian regulator
Gene nameⁱ Official gene symbol, which is typically a short form of the gene name, according to HGNC.	CLOCK (bHLHe8, KAT13D, KIAA0334)
Protein classⁱ Assigned HPA protein class(es) for the encoded protein(s).	Enzymes Metabolic proteins Transcription factors
Protein evidence	Evidence at protein level (all genes)
Number of transcriptsⁱ Number of protein-coding transcripts from the gene as defined by Ensembl.	4
Protein interactions	Interacting with 4 proteins

PROTEIN EXPRESSION AND LOCALIZATION
Tissue profileⁱ A summary of the overall protein expression profile across the analyzed normal tissues based on knowledge-based annotation, presented in the Tissue resource. "Estimation of protein expression could not be performed. View primary data." is shown for genes where available RNA-seq and gene/protein characterization data in combination with immunohistochemistry data has been evaluated as not sufficient to yield a reliable estimation of the protein expression profile.	Ubiquitous nuclear expression.
Subcellular locationⁱ Main subcellular location based on data generated in the subcellular section of the Human Protein Atlas.	Localized to the Nucleoplasm In addition localized to the Vesicles
Predicted locationⁱ All transcripts of all genes have been analyzed regarding the location(s) of corresponding protein based on prediction methods for signal peptides and transmembrane regions. Genes with at least one transcript predicted to encode a secreted protein, according to prediction methods or to UniProt location data, have been further annotated and classified with the aim to determine if the corresponding protein(s) are secreted or actually retained in intracellular locations or membrane-attached. Remaining genes, with no transcript predicted to encode a secreted protein, will be assigned the prediction-based location(s). The annotated location overrules the predicted location, so that a gene encoding a predicted secreted protein that has been annotated as intracellular will have intracellular as the final location.	Intracellular

TISSUE RNA EXPRESSION
Tissue specificityⁱ The RNA specificity category is based on normalized mRNA expression levels in the consensus dataset, calculated from the RNA expression levels in samples from HPA and GTEX. The categories include: tissue enriched, group enriched, tissue enhanced, low tissue specificity and not detected.	Low tissue specificity
Tissue expression clusterⁱ The RNA data was used to cluster genes according to their expression across tissues. Clusters contain genes that have similar expression patterns, and each cluster has been manually annotated to describe common features in terms of function and specificity.	Retina & Testis - Cilium (mainly)
Brain specificityⁱ The regional specificity category is based on mRNA expression levels in the analysed brain samples, grouped into 13 main brain regions and calculated for the three different species. All brain expression profiles are based on data from HPA. The specificity categories include: regionally enriched, group enriched, regionally enhanced, low regional specificity and not detected. The classification rules are the same used for the tissue specificity category	Low human brain regional specificity
Brain expression clusterⁱ The RNA data was used to cluster genes according to their expression across tissues. Clusters contain genes that have similar expression patterns, and each cluster has been manually annotated to describe common features in terms of function and specificity.	Non-specific - Transcription (mainly)

CELL TYPE RNA EXPRESSION
Single cell type specificityⁱ The RNA specificity category is based on mRNA expression levels in the analyzed cell types based on scRNA-seq data from normal tissues. The categories include: cell type enriched, group enriched, cell type enhanced, low cell type specificity and not detected.	Low cell type specificity
Single cell type expression clusterⁱ The RNA data was used to cluster genes according to their expression across single cell types. Clusters contain genes that have similar expression patterns, and each cluster has been manually annotated to describe common features in terms of function and specificity.	Spermatocytes - Spermatogenesis (mainly)
Tissue cell type classificationⁱ Genes can have enriched specificity in different cell types in one or several tissues, or be enriched in a core cell type that appears in many different tissues.	Cell type enriched (Spleen - Endothelial cells, Stomach - Endothelial cells, Testis - Spermatocytes)
Immune cell specificityⁱ The RNA specificity category is based on mRNA expression levels in the analyzed samples based on data from HPA. The categories include: cell type enriched, group enriched, cell type enhanced, low cell type specificity and not detected.	Low immune cell specificity
Immune cell expression clusterⁱ The RNA data was used to cluster genes according to their expression across single cell types. Clusters contain genes that have similar expression patterns, and each cluster has been manually annotated to describe common features in terms of function and specificity.	Non-specific - Unknown function (mainly)

CANCER & CELL LINES
Prognostic summary	CLOCK is a prognostic marker in Kidney renal clear cell carcinoma
Cancer specificityⁱ Specificity of RNA expression in 17 cancer types is categorized as either cancer enriched, group enriched, cancer enhanced, low cancer specificity and not detected.	Low cancer specificity
Cell line expression clusterⁱ The RNA data was used to cluster genes according to their expression across cell lines. Clusters contain genes that have similar expression patterns, and each cluster has been manually annotated to describe common features in terms of function and specificity.	Non-specific - mRNA splicing & Cell cycle (mainly)
Cell line specificityⁱ RNA specificity category based on RNA sequencing data from cancer cell lines in the Human Protein Atlas grouped according to type of cancer. Genes are classified into six different categories (enriched, group enriched, enhanced, low specificity and not detected) according to their RNA expression levels across the panel of cell lines.	Low cancer specificity

PROTEINS IN BLOOD
Detected in blood by immunoassayⁱ The blood-based immunoassay category applies to actively secreted proteins and is based on plasma or serum protein concentrations established with enzyme-linked immunosorbent assays, compiled from a literature search. The categories include: detected and not detected, where detection refers to a concentration found in the literature search.	No (not applicable)
Detected in blood by mass spectrometryⁱ Detection or not of the gene in blood, based on spectral count estimations from a publicly available mass spectrometry-based plasma proteomics data set obtained from the PeptideAtlas.	No
Proximity extension assayⁱ Detectibility in blood, based on proximity extension assays (Olink) for a longitudinal wellness study covering 76 individuals with six visits during two years. Read more	Not available

PROTEIN FUNCTION
Protein function (UniProt)ⁱ Useful information about the protein provided by UniProt.	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, BMAL1, 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 BMAL1 or 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-BMAL1\|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 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-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-BMAL2 heterodimer activates the transcription of SERPINE1/PAI1 and BHLHE40/DEC1. The preferred binding motif for the CLOCK-BMAL1 heterodimer is 5'-CACGTGA-3', which contains a flanking adenine nucleotide at the 3-prime end of the canonical 6-nucleotide E-box sequence 1. CLOCK specifically binds to the half-site 5'-CAC-3', while BMAL1 binds to the half-site 5'-GTGA-3' 2. The CLOCK-BMAL1 heterodimer also recognizes the non-canonical E-box motifs 5'-AACGTGA-3' and 5'-CATGTGA-3' 3. CLOCK has an intrinsic acetyltransferase activity, which enables circadian chromatin remodeling by acetylating histones and nonhistone proteins, including its own partner 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 4. 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 5. Drives the circadian rhythm of blood pressure through transcriptional activation of ATP1B1 (By similarity).... show less
Molecular function (UniProt)ⁱ Keywords assigned by UniProt to proteins due to their particular molecular function.	Activator, Acyltransferase, DNA-binding, Transferase
Biological process (UniProt)ⁱ Keywords assigned by UniProt to proteins because they are involved in a particular biological process.	Biological rhythms, DNA damage, Transcription, Transcription regulation
Gene summary (Entrez)ⁱ Useful information about the gene from Entrez	The protein encoded by this gene plays a central role in the regulation of circadian rhythms. The protein encodes a transcription factor of the basic helix-loop-helix (bHLH) family and contains DNA binding histone acetyltransferase activity. The encoded protein forms a heterodimer with ARNTL (BMAL1) that binds E-box enhancer elements upstream of Period (PER1, PER2, PER3) and Cryptochrome (CRY1, CRY2) genes and activates transcription of these genes. PER and CRY proteins heterodimerize and repress their own transcription by interacting in a feedback loop with CLOCK/ARNTL complexes. Polymorphisms in this gene may be associated with behavioral changes in certain populations and with obesity and metabolic syndrome. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jan 2014]... show less

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