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ARNTL2

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ARNTL2
Available structures
PDBOrtholog search: PDBe RCSB
Identifiers
AliasesARNTL2, BMAL2, CLIF, MOP9, PASD9, bHLHe6, aryl hydrocarbon receptor nuclear translocator like 2
External IDsOMIM: 614517; MGI: 2684845; HomoloGene: 10609; GeneCards: ARNTL2; OMA:ARNTL2 - orthologs
Orthologs
SpeciesHumanMouse
Entrez

56938

272322

Ensembl

ENSG00000029153

ENSMUSG00000040187

UniProt

Q8WYA1

Q2VPD4

RefSeq (mRNA)

NM_172309
NM_001289679
NM_001289680
NM_001289681

RefSeq (protein)

NP_001234931
NP_001234932
NP_001234933
NP_001234934
NP_064568

NP_001276608
NP_001276609
NP_001276610
NP_758513

Location (UCSC)Chr 12: 27.33 – 27.43 MbChr 6: 146.7 – 146.74 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Aryl hydrocarbon receptor nuclear translocator-like 2, also known as Arntl2, Mop9,[5] Bmal2,[6] or Clif,[7] is a gene.

Arntl2 is a paralog to Arntl, which are both homologs of the Drosophila Cycle.[8] Homologs were also isolated in fish,[9] birds[10] and mammals such as mice[11] and humans.[5] Based on phylogenetic analyses, it was proposed that Arntl2 arose from duplication of the Arntl gene early in the vertebrate lineage, followed by rapid divergence of the Arntl gene copy.[11] The protein product of the gene interacts with both CLOCK and NPAS2 to bind to E-box sequences in regulated promoters and activate their transcription.[5] Although Arntl2 is not required for normal function of the mammalian circadian oscillator, it may play an important role in mediating the output of the circadian clock. Perhaps because of this, there is relatively little published literature on the role of Arntl2 in regulation of physiology.

Arntl2 is a candidate gene for human type 1 diabetes.[12]

In overexpression studies, ARNTL2 protein forms a heterodimer with CLOCK to regulate E-box sequences in the Pai-1 promoter.[7] Recent work suggest that this interaction may be in concert with ARNTL/CLOCK heterodimeric complexes.[13]

History

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The ARNTL2 gene was originally discovered in 2000 by John B. Hogenesch et al.[5] under the name MOP9 as a part of the PAS domain superfamily of eukaryotic transcription factors and as a homolog to ARNTL/MOP3. Hogenesch’s initial characterization of MOP9 indicated the role of the MOP9 protein as a partner of the bHLH-PAS transcription factor CLOCK in that the MOP9 protein forms a transcriptionally-active heterodimer with the circadian CLOCK protein. The MOP9 protein, like the MOP3 protein, was also found to form heterodimers with MOP4 and hypoxia-inducible factors including HIF1α. The MOP9 gene was found to be coexpressed with CLOCK in the suprachiasmatic nucleus (SCN) in the hypothalamus, the site of the central mammalian circadian oscillator. Due to MOP9 exhibiting extensive sequence identity with genes such as MOP3 and CYCLE, its dimerization with CLOCK, and the brain-specific expression of MOP9, particularly its expression in the SCN, Hogenesch et al. proposed that MOP9 is involved in the regulation of locomotor activity as a part of the mammalian circadian system. Further studies on the MOP9 gene have adopted the names ARNTL2 and BMAL2 in the same style as the previously-discovered ARNTL gene. Like ARNTL/BMAL1, one of the earliest discovered functions of BMAL2 in the circadian system was through its formation of the BMAL2-CLOCK heterodimer, and the relative transactivation of BMAL2-CLOCK and BMAL1-CLOCK have also indicated that BMAL1 and BMAL2 have distinguishable and individually important roles in the circadian system.[14] Knockout studies of BMAL1 and BMAL2 have also demonstrated the regulatory effect of BMAL1 on BMAL2 expression,[15] and have indicated that BMAL2 may play a more significant role in the circadian system than previously appreciated,[16] although the exact nature of the role of BMAL2 has not yet been fully elucidated.

Structure

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The BMAL2 protein follows the basic helix-loop-helix structure of the PER-ARNT-SIM family[17] and contains a bHLH-PAS domain in its N-terminal region and a variable C-terminus.[6] The PAS domain acts as a dimerization and binding surface in the aryl hydrocarbon receptor (AHR). Overall, BMAL2 shares much of its structure with BMAL1.[18] However, the location on Chromosome 12 of BMAL2 in humans suggests that the gene may have a different function in the embryo.[17]

Function

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BMAL2 forms a heterodimer with CLOCK, and activates transcription, and plays a role in the molecular oscillator. BMAL1 and BMAL2 are positive regulators and activate transcription by binding to proximal (–565 to –560 bp) and distal (–680 to –675 bp) E-box enhancers of the PAI-1 promoter.[13] BMAL 2 functions similarly to BMAL1, but a research study from 2009 found differences in affinities of the homolog genes.[19] The Per2 gene showed a stronger affinity to the BMAL2-CLOCK complex, and CRY2 had a stronger affinity to BMAL1-CLOCK complex. Per2 and CRY2 both inhibit the complexes, and negatively regulate transcription. The true function on Bmal2 is not yet fully understood., A 2010 study by Shi el. al shows that overexpression of BMAL2 in a BMAL1 knockout mice rescues locomotor rhythms and metabolic rhythms.[16] In the same study, rhythmicity was not rescued in peripheral tissues, such as the liver and lung. Bmal2 cannot replace Bmal1, and the two are not interchangeable. The protein does play an active role in the oscillator, but Bmal2 is not required for circadian oscillations in mice.

Interactions

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Protein Mechanism Source
PER1/2/3 Transcription of PER1/2/3 is activated by BMAL2-CLOCK heterodimer, and inhibits the activity of said photodimer. [7]
CRY1/2 Transcription of CRY1/2 is activated by BMAL2-CLOCK heterodimer, and inhibits the activity of said photodimer. [7]
DEC1 Transcription of DEC1 is activated by BMAL2-CLOCK heterodimer, suppresses transcription of DEC2, PER2, and DBP. [20]
PAI1 Transcription of PAI1 is activated by BMAL2-CLOCK heterodimer. [13]
SIRT1 Transcription of SIRT1 is activated by BMAL2-CLOCK heterodimer, inhibits CLOCK/NPAS1-BMAL2 activity and promotes the deacetylation and degradation of PER2. [21]

Species distribution

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Orthologs for BMAL2 have been found in many mammals other than humans, including chimpanzees, dogs and cows (ARNTL2), mice (Arntl2 and Bmal2), and rats (ARNTL2),[22] as well as in zebrafish.[11] ARNTL2 genes differ significantly more between species than ARNTL genes– BMAL2 proteins have diverged 20 times as quickly as BMAL1 proteins since the genes diverged, suggesting an unidentified function in BMAL1 that does not exist in BMAL2. Human and zebrafish BMAL2 proteins contained only 66% of the same amino acids, rather than 85% between human and zebrafish BMAL1 proteins.[11] Identifying the cause of the comparatively significant differences across species in BMAL2 will be significant for understanding the function of BMAL2 in the circadian clock.[11]

Knockout Studies

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Like many genes involved in the circadian system, BMAL2 is a paralog of BMAL1. However, a 2000 study by Bunger et al.[15] demonstrated that unlike other paralog pairs in the circadian system, such as Per1/Per2, Cry1/Cry2, and Clock/Npas2, only a single knockout of either BMAL1 or BMAL2 is required to confer arrhythmicity, rather than a knockout of both paralogs, although other studies have indicated that BMAL1-specific knockouts also have significant effects on metabolism and longevity.[23][24] The same 2000 study by Bunger et al. also indicated that knockouts of BMAL1 down-regulate expression of BMAL2.[15] A 2010 study by Shi et al.[16] found that BMAL2 expression, conferred by a constitutively expressed promoter, can rescue both circadian rhythmicity in locomotion as well as metabolic phenotypes in Bmal1-knockout mice. Thus, BMAL1 and BMAL2 form a functionally redundant paralog pair, but in mice, BMAL2 expression is regulated by BMAL1 such that knocking out BMAL1 effectively results in the knockout of both BMAL1 and BMAL2, indicating that BMAL2 may play a more important role in the circadian system than previously thought. However, this same study by Shi et al.[16] also found that over-expression of BMAL2 is ultimately insufficient to drive circadian rhythms in the peripheral tissues of mice, thereby suggesting that the behavioral rhythms observed in this study may come from weak molecular clocks fortified through networks with the suprachiasmatic nucleus (SCN).

The C-terminal region of the BMAL1 protein is crucial for generating sustained circadian oscillations at the cellular level. Two specific domains within this intrinsically unstructured C-terminus enable this function, distinguishing BMAL1 from BMAL2. The regulation of the BMAL1 transactivation domain (TAD) as a key mechanism in circadian timing is an ongoing area of research.[25]

Clinical significance

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BMAL1 and BMAL2 genes are known to have a role in glucose homeostasis.[26] A research study from 2015[26] used forward genetics to find a genotype of  BMAL2 associated with Type 2 diabetes. The BMAL2 rs7958822 is a polymorphism, and has various genotypes: A/G, A/A, and G/G. The study found an association that obese men with BMAL2 rs7958822 A/G and A/C genotypes had a higher prevalence of type 2 diabetes.

Prior research studies have found desynchronization in cortisol synthesis and body temperature in patients with Parkinson’s Disease, suggesting a role of the circadian genes in the disease,[27] The study used RT-PCR assay to track the BMAL2 gene in PD patients, and found changes in expression, specifically at 21:00 and 00:00. More research is needed to find the molecular mechanism behind this, but the results suggest that BMAL 2 and the molecular clock play a role in Parkinson’s disease.

In colorectal cancer cells, the upregulation of BMAL2 has been associated with higher levels of tumor mutational burden (TMB) as a result of subsequent upregulation of PAI1.[28] The relationship between BMAL2 and TMB has been investigated in many models, providing further evidence for a positive correlation between BMAL2 expression and the expression of promoters of TMB.[29] However, there is still a gap in research investigating the predictive capacity of circadian gene expression, including BMAL2, relating to TMB levels.

See also

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References

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  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000029153 – Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000040187 – Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. ^ a b c d Hogenesch JB, Gu YZ, Moran SM, Shimomura K, Radcliffe LA, Takahashi JS, et al. (July 2000). "The basic helix-loop-helix-PAS protein MOP9 is a brain-specific heterodimeric partner of circadian and hypoxia factors". The Journal of Neuroscience. 20 (13): RC83. doi:10.1523/JNEUROSCI.20-13-j0002.2000. PMC 6772280. PMID 10864977.
  6. ^ a b "BMAL2 Gene - GeneCards | BMAL2 Protein | BMAL2 Antibody". www.genecards.org. Retrieved 2023-04-26.
  7. ^ a b c d Maemura K, de la Monte SM, Chin MT, Layne MD, Hsieh CM, Yet SF, et al. (November 2000). "CLIF, a novel cycle-like factor, regulates the circadian oscillation of plasminogen activator inhibitor-1 gene expression". The Journal of Biological Chemistry. 275 (47): 36847–36851. doi:10.1074/jbc.C000629200. PMID 11018023.
  8. ^ Rutila JE, Suri V, Le M, So WV, Rosbash M, Hall JC (May 1998). "CYCLE is a second bHLH-PAS clock protein essential for circadian rhythmicity and transcription of Drosophila period and timeless". Cell. 93 (5): 805–814. doi:10.1016/S0092-8674(00)81441-5. PMID 9630224. S2CID 18175560.
  9. ^ Cermakian N, Whitmore D, Foulkes NS, Sassone-Corsi P (April 2000). "Asynchronous oscillations of two zebrafish CLOCK partners reveal differential clock control and function". Proceedings of the National Academy of Sciences of the United States of America. 97 (8): 4339–4344. Bibcode:2000PNAS...97.4339C. doi:10.1073/pnas.97.8.4339. PMC 18243. PMID 10760301.
  10. ^ Okano T, Yamamoto K, Okano K, Hirota T, Kasahara T, Sasaki M, et al. (September 2001). "Chicken pineal clock genes: implication of BMAL2 as a bidirectional regulator in circadian clock oscillation". Genes to Cells. 6 (9): 825–836. doi:10.1046/j.1365-2443.2001.00462.x. PMID 11554928. S2CID 45261835.
  11. ^ a b c d e Okano T, Sasaki M, Fukada Y (March 2001). "Cloning of mouse BMAL2 and its daily expression profile in the suprachiasmatic nucleus: a remarkable acceleration of Bmal2 sequence divergence after Bmal gene duplication". Neuroscience Letters. 300 (2): 111–114. doi:10.1016/S0304-3940(01)01581-6. PMID 11207387. S2CID 27706733.
  12. ^ Hung MS, Avner P, Rogner UC (September 2006). "Identification of the transcription factor ARNTL2 as a candidate gene for the type 1 diabetes locus Idd6". Human Molecular Genetics. 15 (18): 2732–2742. doi:10.1093/hmg/ddl209. PMID 16893914.
  13. ^ a b c Schoenhard JA, Smith LH, Painter CA, Eren M, Johnson CH, Vaughan DE (May 2003). "Regulation of the PAI-1 promoter by circadian clock components: differential activation by BMAL1 and BMAL2". Journal of Molecular and Cellular Cardiology. 35 (5): 473–481. doi:10.1016/S0022-2828(03)00051-8. PMID 12738229.
  14. ^ Sasaki M, Yoshitane H, Du NH, Okano T, Fukada Y (September 2009). "Preferential inhibition of BMAL2-CLOCK activity by PER2 reemphasizes its negative role and a positive role of BMAL2 in the circadian transcription". The Journal of Biological Chemistry. 284 (37): 25149–25159. doi:10.1074/jbc.M109.040758. PMC 2757218. PMID 19605937.
  15. ^ a b c Bunger MK, Wilsbacher LD, Moran SM, Clendenin C, Radcliffe LA, Hogenesch JB, et al. (December 2000). "Mop3 is an essential component of the master circadian pacemaker in mammals". Cell. 103 (7): 1009–1017. doi:10.1016/s0092-8674(00)00205-1. PMC 3779439. PMID 11163178. S2CID 10242426.
  16. ^ a b c d Shi S, Hida A, McGuinness OP, Wasserman DH, Yamazaki S, Johnson CH (February 2010). "Circadian clock gene Bmal1 is not essential; functional replacement with its paralog, Bmal2". Current Biology. 20 (4): 316–321. Bibcode:2010CBio...20..316S. doi:10.1016/j.cub.2009.12.034. PMC 2907674. PMID 20153195.
  17. ^ a b Schoenhard JA, Eren M, Johnson CH, Vaughan DE (July 2002). "Alternative splicing yields novel BMAL2 variants: tissue distribution and functional characterization". American Journal of Physiology. Cell Physiology. 283 (1): C103 – C114. doi:10.1152/ajpcell.00541.2001. PMID 12055078.
  18. ^ Shi S, Hida A, McGuinness OP, Wasserman DH, Yamazaki S, Johnson CH (February 2010). "Circadian clock gene Bmal1 is not essential; functional replacement with its paralog, Bmal2". Current Biology. 20 (4): 316–321. Bibcode:2010CBio...20..316S. doi:10.1016/j.cub.2009.12.034. PMC 2907674. PMID 20153195. S2CID 18752396.
  19. ^ Sasaki M, Yoshitane H, Du NH, Okano T, Fukada Y (September 2009). "Preferential inhibition of BMAL2-CLOCK activity by PER2 reemphasizes its negative role and a positive role of BMAL2 in the circadian transcription". The Journal of Biological Chemistry. 284 (37): 25149–25159. doi:10.1074/jbc.m109.040758. PMC 2757218. PMID 19605937.
  20. ^ Kawamoto T, Noshiro M, Sato F, Maemura K, Takeda N, Nagai R, et al. (January 2004). "A novel autofeedback loop of Dec1 transcription involved in circadian rhythm regulation". Biochemical and Biophysical Research Communications. 313 (1): 117–124. doi:10.1016/j.bbrc.2003.11.099. PMID 14672706.
  21. ^ Asher G, Gatfield D, Stratmann M, Reinke H, Dibner C, Kreppel F, et al. (July 2008). "SIRT1 regulates circadian clock gene expression through PER2 deacetylation". Cell. 134 (2): 317–328. doi:10.1016/j.cell.2008.06.050. PMID 18662546. S2CID 17267748.
  22. ^ Stelzer G, Rosen N, Plaschkes I, Zimmerman S, Twik M, Fishilevich S, et al. (June 2016). "The GeneCards Suite: From Gene Data Mining to Disease Genome Sequence Analyses". Current Protocols in Bioinformatics. 54 (1): 1.30.1–1.30.33. doi:10.1002/cpbi.5. PMID 27322403. S2CID 26619932.
  23. ^ Rudic RD, McNamara P, Curtis AM, Boston RC, Panda S, Hogenesch JB, et al. (November 2004). "BMAL1 and CLOCK, two essential components of the circadian clock, are involved in glucose homeostasis". PLOS Biology. 2 (11): e377. doi:10.1371/journal.pbio.0020377. PMC 524471. PMID 15523558. S2CID 8816869.
  24. ^ Kondratov RV, Kondratova AA, Gorbacheva VY, Vykhovanets OV, Antoch MP (July 2006). "Early aging and age-related pathologies in mice deficient in BMAL1, the core componentof the circadian clock". Genes & Development. 20 (14): 1868–1873. doi:10.1101/gad.1432206. PMC 1522083. PMID 16847346. S2CID 13350374.
  25. ^ Xu H, Gustafson CL, Sammons PJ, Khan SK, Parsley NC, Ramanathan C, et al. (June 2015). "Cryptochrome 1 regulates the circadian clock through dynamic interactions with the BMAL1 C terminus". Nature Structural & Molecular Biology. 22 (6): 476–484. doi:10.1038/nsmb.3018. PMC 4456216. PMID 25961797.
  26. ^ a b Yamaguchi M, Uemura H, Arisawa K, Katsuura-Kamano S, Hamajima N, Hishida A, et al. (December 2015). "Association between brain-muscle-ARNT-like protein-2 (BMAL2) gene polymorphism and type 2 diabetes mellitus in obese Japanese individuals: A cross-sectional analysis of the Japan Multi-institutional Collaborative Cohort Study". Diabetes Research and Clinical Practice. 110 (3): 301–308. doi:10.1016/j.diabres.2015.10.009. PMID 26497775.
  27. ^ Ding H, Liu S, Yuan Y, Lin Q, Chan P, Cai Y (July 2011). "Decreased expression of Bmal2 in patients with Parkinson's disease". Neuroscience Letters. 499 (3): 186–188. doi:10.1016/j.neulet.2011.05.058. PMID 21658431. S2CID 25146780.
  28. ^ Mazzoccoli G, Pazienza V, Panza A, Valvano MR, Benegiamo G, Vinciguerra M, et al. (March 2012). "ARNTL2 and SERPINE1: potential biomarkers for tumor aggressiveness in colorectal cancer". Journal of Cancer Research and Clinical Oncology. 138 (3): 501–511. doi:10.1007/s00432-011-1126-6. PMID 22198637. S2CID 8998806.
  29. ^ Oishi K, Miyazaki K, Uchida D, Ohkura N, Wakabayashi M, Doi R, et al. (April 2009). "PERIOD2 is a circadian negative regulator of PAI-1 gene expression in mice". Journal of Molecular and Cellular Cardiology. 46 (4): 545–552. doi:10.1016/j.yjmcc.2009.01.001. PMID 19168071.
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