BTG2

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BTG family, member 2
Protein BTG2 PDB 3DJU.png
Rendering based on PDB 3DJU.
Available structures
PDB Ortholog search: PDBe, RCSB
Identifiers
Symbols BTG2 ; PC3; TIS21
External IDs OMIM601597 MGI108384 HomoloGene31406 GeneCards: BTG2 Gene
RNA expression pattern
PBB GE BTG2 201236 s at tn.png
PBB GE BTG2 201235 s at tn.png
More reference expression data
Orthologs
Species Human Mouse
Entrez 7832 12227
Ensembl ENSG00000159388 ENSMUSG00000020423
UniProt P78543 Q04211
RefSeq (mRNA) NM_006763 NM_007570
RefSeq (protein) NP_006754 NP_031596
Location (UCSC) Chr 1:
203.27 – 203.28 Mb
Chr 1:
134.08 – 134.08 Mb
PubMed search [1] [2]

Protein BTG2 also known as BTG family member 2 or NGF-inducible anti-proliferative protein PC3 or NGF-inducible protein TIS21, is a protein that in humans is encoded by the BTG2 gene (B-cell translocation gene 2)[1] and in other mammals by the homologous Btg2 gene.[2][3] This protein controls cell cycle progression and proneural genes expression by acting as a transcription coregulator that enhances or inhibits the activity of transcription factors.

The protein BTG2 is the human homolog of the PC3 (pheochromocytoma cell 3) protein in rat and of the Tis21 (tetradecanoyl phorbol acetate-inducible sequence 21) protein in mouse.[4][5] Tis21 had been originally isolated as a sequence induced by TPA in mouse fibroblasts,[3] whereas PC3 was originally isolated as sequence induced at the beginning of neuron differentiation;[2] BTG2 was then isolated in human cells as sequence induced by p53 and DNA damage.[1][6]

The protein encoded by the gene BTG2 (which is the official name assigned to the gene PC3/Tis21/BTG2) is a member of the BTG/Tob family (that comprises six proteins BTG1, BTG2/PC3/Tis21, BTG3/ANA, BTG4/PC3B, Tob1/Tob and Tob2).[4][5][7] This family has structurally related proteins that appear to have antiproliferative properties. In particular, the BTG2 protein has been shown to negatively control a cell cycle checkpoint at the G1 to S phase transition in fibroblasts and neuronal cells by direct inhibition of the activity of cyclin D1 promoter.[8][9][10]

BTG2, essential regulator of neuron differentiation[edit]

A number of studies in vivo have shown that BTG2 expression is associated with the neurogenic asymmetric division in neural progenitor cells.[11][12][13][14][15] Moreover, when directly overexpressed in vivo in neural progenitor cells, BTG2 induces their differentiation.[16][17] In fact, in the neuronal PC12 cell line BTG2 is not able to trigger differentiation by itself, but only to synergize with NGF,[18][19] while in vivo BTG2 is fully able to induce differentiation of progenitor cells, i.e., during embryonic development in the neuroblast of the neural tube and in granule precursors of cerebellum, as well in adult progenitor cells of the dentate gyrus and of the subventricular zone.[16][17] Notably, it has recently been shown that BTG2 is essential for the differentiation of new neurons, using a BTG2 knock out mouse.[20] BTG2 is thus a pan-neural gene required for the development of the new neuron generated during adulthood, in the two neurogenic regions of adult brain, i.e., the hippocampus and the subventricular zone.[20] Such requirement of BTG2 in neuron maturation is consistent with the fact that during brain development BTG2 is expressed in the proliferating neuroblasts of the ventricular zone of the neural tube, and to a lower extent in the differentiating neuroblasts of the mantle zone; postnatally it is expressed in cerebellar precursors mainly in the proliferating regions of the neuropithelium (i.e., in the external granular layer), and in the hippocampus in proliferating and differentiating progenitor cells.[11][16][17] The pro-differentiative action of BTG2 appears to be consequent not only to inhibition of cell cycle progression but also to a BTG2-dependent activation of proneural genes in neural progenitor cells.[16][20] In fact, BTG2 activates proneural genes by associating with the promoter of Id3, a key inhibitor of proneural gene activity, and by negatively regulating its activity.[20]

BTG2 is a transcriptional cofactor, given that it has been shown to associate with, and regulate the promoters not only of Id3 but also of cyclin D1 and RAR-β, being part of transcriptional complexes.[10][21][22] Interestingly, it has been shown that when the differentiation of new neurons of the hippocampus - a brain region important for learning and memory - is either accelerated or delayed by means of overexpression or deletion of BTG2, respectively, spatial and contextual memory is heavily altered.[17][20] This suggests that the time the young neurons spend in different states of neuronal differentiation is critical for their ultimate function in learning and memory, and that BTG2 may play a role in the timing of recruitment of the new neuron into memory circuits.[17][20]

In conclusion, the main action of Btg2 on neural progenitor cells of the dentate gyrus and subventricular zone during adult neurogenesis is the positive control of their terminal differentiation. In contrast, BTG1, the closest homolog to Btg2, appears to negatively regulate the proliferation of adult stem cells in the dentate gyrus and subventricular zone, maintaining in quiescence the stem cells pool and preserving it from depletion (;[23] see for review:[24]).

BTG2 is a medulloblastoma suppressor[edit]

BTG2 has been shown to inhibit medulloblastoma, the very aggressive tumor of cerebellum, by inhibiting the proliferation and triggering the diffentiation of the precursors of cerebellar granule neurons. This demonstration was obtained by overexpressing BTG2 in a mouse model of medulloblastoma, presenting activation of the Sonic Hedgehog pathway (heterozygous for the gene Patched1).[10] More recently, it has been shown that the ablation of BTG2 greatly enhances the medulloblastoma frequency by inhibiting the migration of cerebellar granule neuron precursors. This impairment of migration of the precursors of cerebellar granule neurons forces them to remain at the surface of the cerebellum, where they continue to proliferate, becoming target of transforming insults.[25] The impairment of migration of the precursors of cerebellar granule neurons (GCPs) depends on the inhibition of expression of the chemokine CXCL3 consequent to ablation of BTG2. In fact, the transcription of CXCL3 is directly regulated by BTG2, and CXCL3 is able to induce cell-autonomously the migration of cerebellar granule precursors. Remarkably, the treatment with CXCL3 reduces the area of medulloblastoma lesions. Thus, CXCL3 is a potential target for medulloblastoma therapy.[25]

Interactions[edit]

BTG2 has been shown to interact with PRMT1,[22] HOXB9,[26][27] CNOT8[28] and HDAC1 and HDAC4.[10]

References[edit]

  1. ^ a b Rouault JP, Falette N, Guéhenneux F, Guillot C, Rimokh R, Wang Q, Berthet C, Moyret-Lalle C, Savatier P, Pain B, Shaw P, Berger R, Samarut J, Magaud JP, Ozturk M, Samarut C, Puisieux A (December 1996). "Identification of BTG2, an antiproliferative p53-dependent component of the DNA damage cellular response pathway". Nat. Genet. 14 (4): 482–6. doi:10.1038/ng1296-482. PMID 8944033. 
  2. ^ a b Bradbury A, Possenti R, Shooter EM, Tirone F (April 1991). "Molecular cloning of PC3, a putatively secreted protein whose mRNA is induced by nerve growth factor and depolarization". Proc. Natl. Acad. Sci. U.S.A. 88 (8): 3353–7. doi:10.1073/pnas.88.8.3353. PMC 51445. PMID 1849653. 
  3. ^ a b Fletcher BS, Lim RW, Varnum BC, Kujubu DA, Koski RA, Herschman HR (August 1991). "Structure and expression of TIS21, a primary response gene induced by growth factors and tumor promoters". J. Biol. Chem. 266 (22): 14511–8. PMID 1713584. 
  4. ^ a b Matsuda S, Rouault J, Magaud J, Berthet C (May 2001). "In search of a function for the TIS21/PC3/BTG1/TOB family". FEBS Lett. 497 (2-3): 67–72. doi:10.1016/S0014-5793(01)02436-X. PMID 11377414. 
  5. ^ a b Tirone F (May 2001). "The gene PC3(TIS21/BTG2), prototype member of the PC3/BTG/TOB family: regulator in control of cell growth, differentiation, and DNA repair?". J. Cell. Physiol. 187 (2): 155–65. doi:10.1002/jcp.1062. PMID 11267995. 
  6. ^ "Entrez Gene: BTG2 BTG family, member 2". 
  7. ^ Winkler GS (January 2010). "The mammalian anti-proliferative BTG/Tob protein family". J. Cell. Physiol. 222 (1): 66–72. doi:10.1002/jcp.21919. PMID 19746446. 
  8. ^ Montagnoli A, Guardavaccaro D, Starace G, Tirone F (October 1996). "Overexpression of the nerve growth factor-inducible PC3 immediate early gene is associated with growth inhibition". Cell Growth Differ. 7 (10): 1327–36. PMID 8891336. 
  9. ^ Guardavaccaro D, Corrente G, Covone F, Micheli L, D'Agnano I, Starace G, Caruso M, Tirone F (March 2000). "Arrest of G(1)-S progression by the p53-inducible gene PC3 is Rb dependent and relies on the inhibition of cyclin D1 transcription". Mol. Cell. Biol. 20 (5): 1797–815. doi:10.1128/MCB.20.5.1797-1815.2000. PMC 85361. PMID 10669755. 
  10. ^ a b c d Farioli-Vecchioli S, Tanori M, Micheli L, Mancuso M, Leonardi L, Saran A, Ciotti MT, Ferretti E, Gulino A, Pazzaglia S, Tirone F (July 2007). "Inhibition of medulloblastoma tumorigenesis by the antiproliferative and pro-differentiative gene PC3". FASEB J. 21 (9): 2215–25. doi:10.1096/fj.06-7548com. PMID 17371797. 
  11. ^ a b Iacopetti P, Barsacchi G, Tirone F, Maffei L, Cremisi F (August 1994). "Developmental expression of PC3 gene is correlated with neuronal cell birthday". Mech. Dev. 47 (2): 127–37. doi:10.1016/0925-4773(94)90085-X. PMID 7811636. 
  12. ^ Iacopetti P, Michelini M, Stuckmann I, Oback B, Aaku-Saraste E, Huttner WB (April 1999). "Expression of the antiproliferative gene TIS21 at the onset of neurogenesis identifies single neuroepithelial cells that switch from proliferative to neuron-generating division". Proc. Natl. Acad. Sci. U.S.A. 96 (8): 4639–44. doi:10.1073/pnas.96.8.4639. PMC 16385. PMID 10200315. 
  13. ^ Haubensak W, Attardo A, Denk W, Huttner WB (March 2004). "Neurons arise in the basal neuroepithelium of the early mammalian telencephalon: a major site of neurogenesis". Proc. Natl. Acad. Sci. U.S.A. 101 (9): 3196–201. doi:10.1073/pnas.0308600100. PMC 365766. PMID 14963232. 
  14. ^ Calegari F, Haubensak W, Haffner C, Huttner WB (July 2005). "Selective lengthening of the cell cycle in the neurogenic subpopulation of neural progenitor cells during mouse brain development". J. Neurosci. 25 (28): 6533–8. doi:10.1523/JNEUROSCI.0778-05.2005. PMID 16014714. 
  15. ^ Götz M, Huttner WB (October 2005). "The cell biology of neurogenesis". Nat. Rev. Mol. Cell Biol. 6 (10): 777–88. doi:10.1038/nrm1739. PMID 16314867. 
  16. ^ a b c d Canzoniere D, Farioli-Vecchioli S, Conti F, Ciotti MT, Tata AM, Augusti-Tocco G, Mattei E, Lakshmana MK, Krizhanovsky V, Reeves SA, Giovannoni R, Castano F, Servadio A, Ben-Arie N, Tirone F (March 2004). "Dual control of neurogenesis by PC3 through cell cycle inhibition and induction of Math1". J. Neurosci. 24 (13): 3355–69. doi:10.1523/JNEUROSCI.3860-03.2004. PMID 15056715. 
  17. ^ a b c d e Farioli-Vecchioli S, Saraulli D, Costanzi M, Pacioni S, Cinà I, Aceti M, Micheli L, Bacci A, Cestari V, Tirone F (October 2008). Goodell, Margaret A., ed. "The timing of differentiation of adult hippocampal neurons is crucial for spatial memory". PLoS Biol. 6 (10): e246. doi:10.1371/journal.pbio.0060246. PMC 2561078. PMID 18842068. 
  18. ^ Corrente G, Guardavaccaro D, Tirone F (March 2002). "PC3 potentiates NGF-induced differentiation and protects neurons from apoptosis". NeuroReport 13 (4): 417–22. doi:10.1097/00001756-200203250-00011. PMID 11930152. 
  19. ^ el-Ghissassi F, Valsesia-Wittmann S, Falette N, Duriez C, Walden PD, Puisieux A (October 2002). "BTG2(TIS21/PC3) induces neuronal differentiation and prevents apoptosis of terminally differentiated PC12 cells". Oncogene 21 (44): 6772–78. doi:10.1038/sj.onc.1205888. PMID 12360398. 
  20. ^ a b c d e f Farioli-Vecchioli S, Saraulli D, Costanzi M, Leonardi L, Cinà I, Micheli L, Nutini M, Longone P, Oh SP, Cestari V, Tirone F (2009). Okazawa, Hitoshi, ed. "Impaired terminal differentiation of hippocampal granule neurons and defective contextual memory in PC3/Tis21 knockout mice". PLoS ONE 4 (12): e8339. doi:10.1371/journal.pone.0008339. PMC 2791842. PMID 20020054. 
  21. ^ Passeri D, Marcucci A, Rizzo G, Billi M, Panigada M, Leonardi L, Tirone F, Grignani F (July 2006). "Btg2 enhances retinoic acid-induced differentiation by modulating histone H4 methylation and acetylation". Mol. Cell. Biol. 26 (13): 5023–32. doi:10.1128/MCB.01360-05. PMC 1489145. PMID 16782888. 
  22. ^ a b Lin WJ, Gary JD, Yang MC, Clarke S, Herschman HR (June 1996). "The mammalian immediate-early TIS21 protein and the leukemia-associated BTG1 protein interact with a protein-arginine N-methyltransferase". J. Biol. Chem. 271 (25): 15034–44. doi:10.1074/jbc.271.25.15034. PMID 8663146. 
  23. ^ Farioli-Vecchioli S, Micheli L, Saraulli D, Ceccarelli M, Cannas S, Scardigli R, Leonardi L, Cinà I, Costanzi M, Ciotti MT, Moreira P, Rouault J-P, Cestari V & Tirone F (2012). "Btg1 is Required to Maintain the Pool of Stem and Progenitor Cells of the Dentate Gyrus and Subventricular Zone". Frontiers in Neuroscience 6: 124. doi:10.3389/fnins.2012.00124. PMC 3431174. PMID 22969701. 
  24. ^ Tirone F, Farioli-Vecchioli S, Micheli L, Ceccarelli M & Leonardi L (2013). "Genetic control of adult neurogenesis: interplay of differentiation, proliferation and survival modulates new neurons function, and memory circuits". Frontiers in cellular neuroscience 7: 59. doi:10.3389/fncel.2013.00059. PMC 3653098. PMID 23734097. 
  25. ^ a b Farioli-Vecchioli S, Cinà I, Ceccarelli M, Micheli L, Leonardi L, Ciotti MT, De Bardi M, Di Rocco C, Pallini R, Cavallaro S, Tirone F (October 2012). "Tis21 knock-out enhances the frequency of medulloblastoma in patched1 heterozygous mice by inhibiting the CXCL3-dependent migration of cerebellar neurons". The Journal of neuroscience : the official journal of the Society for Neuroscience 32 (44): 15547–15564. doi:10.1523/JNEUROSCI.0412-12.2012. PMID 23115191. 
  26. ^ Prévôt D, Voeltzel T, Birot AM, Morel AP, Rostan MC, Magaud JP, Corbo L (January 2000). "The leukemia-associated protein Btg1 and the p53-regulated protein Btg2 interact with the homeoprotein Hoxb9 and enhance its transcriptional activation". J. Biol. Chem. 275 (1): 147–53. doi:10.1074/jbc.275.1.147. PMID 10617598. 
  27. ^ Berthet C, Guéhenneux F, Revol V, Samarut C, Lukaszewicz A, Dehay C, Dumontet C, Magaud JP, Rouault JP (January 2002). "Interaction of PRMT1 with BTG/TOB proteins in cell signalling: molecular analysis and functional aspects". Genes Cells 7 (1): 29–39. doi:10.1046/j.1356-9597.2001.00497.x. PMID 11856371. 
  28. ^ Prévôt D, Morel AP, Voeltzel T, Rostan MC, Rimokh R, Magaud JP, Corbo L (March 2001). "Relationships of the antiproliferative proteins BTG1 and BTG2 with CAF1, the human homolog of a component of the yeast CCR4 transcriptional complex: involvement in estrogen receptor alpha signaling pathway". J. Biol. Chem. 276 (13): 9640–8. doi:10.1074/jbc.M008201200. PMID 11136725. 

Further reading[edit]