The PER3 gene encodes the period circadian protein homolog 3 protein in humans. [5] PER3 is a paralog to the PER1 and PER2 genes. It is a circadian gene associate with delayed sleep phase syndrome in humans. [6]
The PER3 gene encodes the period circadian protein homolog 3 protein in humans. [5] PER3 is a paralog to the PER1 and PER2 genes. It is a circadian gene associate with delayed sleep phase syndrome in humans. [6]
The Per3 gene was independently cloned by two research groups (Kobe University School of Medicine and the Harvard Medical School) who both published their discovery in June 1998. [7] [8] The mammalian Per3 was discovered by searching for homologous cDNA sequences to Per2. The amino acid sequence of the mouse PERIOD3 protein (mPER3) is between 37-56% similar to the other two PER proteins. [8] [7]
This gene is a member of the Period family of genes. It is expressed in a circadian pattern in the suprachiasmatic nucleus (SCN), the primary circadian pacemaker in the mammalian brain. Genes in this family encode components of the circadian rhythms of locomotor activity, metabolism, and behavior. Circadian expression in the SCN continues in constant darkness, and a shift in the light/dark cycle evokes a proportional shift of gene expression in the SCN. [9] PER1 and PER2 are necessary for molecular timekeeping and light responsiveness in the master circadian clock in the SCN, but little data is shown on the concrete function for PER3. PER3 was found to be important for endogenous timekeeping in specific tissues and those tissue-specific changes in endogenous periods result in internal misalignment of circadian clocks in Per3 double knockout (-/-) mice. [10] PER3 may have a stabilizing effect on PER1 and PER2, and this stabilizing effect may be reduced in the PER3-P415A/H417R polymorphism. [11]
The RNA levels of mPer3 oscillate with a circadian rhythm in both the SCN and in the eyes, as well as in peripheral tissues, including the liver, skeletal muscle, and testis. [8] Unlike Per1 and Per2, of which the mRNA is induced in response to light, Per3 mRNA in the SCN does not respond to light. This suggests that Per3 may be regulated differently than either Per1 or Per2. [8]
The mPER3 protein contains a PAS domain, similar to mPER1 and mPER2. Likely, mPER3 binds to other proteins using this domain. [8] However, while PER1/2 have been shown to be important in the transcription-translation feedback loop involved in the intracellular circadian clock, the influence of PER3 in this loop has not yet been fully elucidated, given that mPER3 does not appear to be functionally redundant to mPER1 and mPER2. [12] mPer3 may not be a member of the core clock loop at all. [12]
While the Per3 gene is a paralog to the PER1 and PER2 genes, studies in animals generally show that it does not contribute significantly to circadian rhythms. Functional Per3-/- animals experience only small changes in free-running period, [12] and do not respond significantly differently to light pulses. [13] Per1-/- and Per2-/- animals experience a significant change in free-running period; however, knocking out Per3 in addition to either Per1 or Per2 has little effect on free-running rhythms. [12] Furthermore, Per1-/-Per2-/- mice are completely arrhythmic, indicating that these two genes have much more importance to the biological clock than Per3. [12]
Per3 knockout mice experience a slightly shortened period of locomotor activity (by 0.5 hr [13] ) and are less sensitive to light, in that they entrain more slowly to changes in the light-dark cycle. PER3 may be involved in the suppression of behavioral activity in response to light, although mPer3 expression is not necessary for circadian rhythms. [14] [15]
The PER3 “length” polymorphism in the 54-bp repeat sequence in exon 18 (GenBank accession no. AB047686) is a structural polymorphism due to an insertion or deletion of 18 amino acids in a region encoding a putative phosphorylation domain. The polymorphism has been associated with diurnal preference and delayed sleep phase syndrome. A longer allele polymorphism is associated with “morningness” and the short allele with “eveningness.” The short allele is also associated with delayed sleep phase syndrome. [6] The length polymorphism has also been shown to inhibit adipogenesis and Per3 knockout mice were shown to have increased adipose tissue and decreased muscle tissue compared to wild type. Additionally, the presence of the length polymorphism has also been shown to be associated with type 2 diabetes mellitus (T2DM) patients as compared to non-diabetic control patients. [16] The PER3-P415A/H417R polymorphism has been linked to familial advanced sleep phase syndrome in humans, as well as to seasonal affective disorder, though when knocked in to mice, the polymorphism causes a delayed sleep phase. [11]
The following is a list of some orthologs of the PER3 gene in other species: [17]
The human PER3 gene is located on chromosome 1 at the following location: [18]
PER3 has 19 transcripts (splice variants).
The PER3 protein has been identified to have the following features: [19]
The following are some known post transcriptional modifications to the Per3 gene: [19]
A circadian rhythm, or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism and responds to the environment. These 24-hour rhythms are driven by a circadian clock, and they have been widely observed in animals, plants, fungi and cyanobacteria.
Advanced Sleep Phase Disorder (ASPD), also known as the advanced sleep-phase type (ASPT) of circadian rhythm sleep disorder, is a condition that is characterized by a recurrent pattern of early evening sleepiness and early morning awakening. This sleep phase advancement can interfere with daily social and work schedules, and results in shortened sleep duration and excessive daytime sleepiness. The timing of sleep and melatonin levels are regulated by the body's central circadian clock, which is located in the suprachiasmatic nucleus in the hypothalamus.
The suprachiasmatic nucleus or nuclei (SCN) is a tiny region of the brain in the hypothalamus, situated directly above the optic chiasm. It is responsible for controlling circadian rhythms. The neuronal and hormonal activities it generates regulate many different body functions in a 24-hour cycle. The mouse SCN contains approximately 20,000 neurons.
Melatonin receptors are G protein-coupled receptors (GPCR) which bind melatonin. Three types of melatonin receptors have been cloned. The MT1 (or Mel1A or MTNR1A) and MT2 (or Mel1B or MTNR1B) receptor subtypes are present in humans and other mammals, while an additional melatonin receptor subtype MT3 (or Mel1C or MTNR1C) has been identified in amphibia and birds. The receptors are crucial in the signal cascade of melatonin. In the field of chronobiology, melatonin has been found to be a key player in the synchrony of biological clocks. Melatonin secretion by the pineal gland has circadian rhythmicity regulated by the suprachiasmatic nucleus (SCN) found in the brain. The SCN functions as the timing regulator for melatonin; melatonin then follows a feedback loop to decrease SCN neuronal firing. The receptors MT1 and MT2 control this process. Melatonin receptors are found throughout the body in places such as the brain, the retina of the eye, the cardiovascular system, the liver and gallbladder, the colon, the skin, the kidneys, and many others. In 2019, X-ray crystal and cryo-EM structures of MT1 and MT2 were reported.
CLOCK or Clock is a gene encoding a basic helix-loop-helix-PAS transcription factor that is believed to affect both the persistence and period of circadian rhythms.
Timeless (tim) is a gene in multiple species but is most notable for its role in Drosophila for encoding TIM, an essential protein that regulates circadian rhythm. Timeless mRNA and protein oscillate rhythmically with time as part of a transcription-translation negative feedback loop involving the period (per) gene and its protein.
Period (per) is a gene located on the X chromosome of Drosophila melanogaster. Oscillations in levels of both per transcript and its corresponding protein PER have a period of approximately 24 hours and together play a central role in the molecular mechanism of the Drosophila biological clock driving circadian rhythms in eclosion and locomotor activity. Mutations in the per gene can shorten (perS), lengthen (perL), and even abolish (per0) the period of the circadian rhythm.
Neuronal PAS domain protein 2 (NPAS2) also known as member of PAS protein 4 (MOP4) is a transcription factor protein that in humans is encoded by the NPAS2 gene. NPAS2 is paralogous to CLOCK, and both are key proteins involved in the maintenance of circadian rhythms in mammals. In the brain, NPAS2 functions as a generator and maintainer of mammalian circadian rhythms. More specifically, NPAS2 is an activator of transcription and translation of core clock and clock-controlled genes through its role in a negative feedback loop in the suprachiasmatic nucleus (SCN), the brain region responsible for the control of circadian rhythms.
PER2 is a protein in mammals encoded by the PER2 gene. PER2 is noted for its major role in circadian rhythms.
The PER1 gene encodes the period circadian protein homolog 1 protein in humans.
Aryl hydrocarbon receptor nuclear translocator-like protein 1 (ARNTL) or Brain and Muscle ARNT-Like 1 (BMAL1) is a protein that in humans is encoded by the Bmal1 gene, also known as ARNTL, MOP3, and, less commonly, BHLHE5, BMAL, BMAL1C, JAP3, PASD3, and TIC.
In molecular biology, an oscillating gene is a gene that is expressed in a rhythmic pattern or in periodic cycles. Oscillating genes are usually circadian and can be identified by periodic changes in the state of an organism. Circadian rhythms, controlled by oscillating genes, have a period of approximately 24 hours. For example, plant leaves opening and closing at different times of the day or the sleep-wake schedule of animals can all include circadian rhythms. Other periods are also possible, such as 29.5 days resulting from circalunar rhythms or 12.4 hours resulting from circatidal rhythms. Oscillating genes include both core clock component genes and output genes. A core clock component gene is a gene necessary for to the pacemaker. However, an output oscillating gene, such as the AVP gene, is rhythmic but not necessary to the pacemaker.
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This article incorporates text from the United States National Library of Medicine, which is in the public domain.