The gene PC3(TIS21/BTG2), prototype member of the PC3/BTG/TOB family: regulator in control of cell growth, differentiation, and DNA repair?
PC3(TIS21/BTG2) is the founding member of a family of genes endowed with antiproliferative properties, namely BTG1, ANA/BTG3, PC3B, TOB, and TOB2. PC3 was originally isolated as a gene induced by nerve growth factor during neuronal differentiation of rat PC12 cells, or by TPA in NIH3T3 cells (named TIS21), and is a marker for neuronal birth in vivo. This and other findings suggested its implication in the process of neurogenesis as mediator of the growth arrest before differentiation. Remarkably, its human homolog, named BTG2, was shown to be p53-inducible, in conditions of genotoxic damage. PC3(TIS21/BTG2) impairs G(1)-S progression, either by a Rb-dependent pathway through inhibition of cyclin D1 transcription, or in a Rb-independent fashion by cyclin E downregulation. PC3(TIS21/BTG2) might also control the G(2) checkpoint. Furthermore, PC3(TIS21/BTG2) interacts with carbon catabolite repressor protein-associated factor 1 (CAF-1), a molecule that associates to the yeast transcriptional complex CCR4 and might influence cell cycle, with the transcription factor Hoxb9, and with the protein-arginine methyltransferase 1, that might control transcription through histone methylation. Current evidence suggests a physiological role of PC3(TIS21/BTG2) in the control of cell cycle arrest following DNA damage and other types of cellular stress, or before differentiation of the neuron and other cell types. The molecular function of PC3(TIS21/BTG2) is still unknown, but its ability to modulate cyclin D1 transcription, or to synergize with the transcription factor Hoxb9, suggests that it behaves as a transcriptional co-regulator.
Consiglio Nazionale delle Ricerche, Istituto di Neurobiologia, Rome, Italy. tirone@mercury.itbm.rm.cnr.it
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D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D002455:Cell Division / Q000235:genetics; D004260:DNA Repair / Q000502:physiology*; D016147:Genes, Tumor Suppressor; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics* / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D025521:Tumor Suppressor Proteins
C415579:BTG4 protein, human; C489435:Btg2 protein, mouse; C485928:Btg4 protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D017874:Immediate-Early Proteins; D047908:Intracellular Signaling Peptides and Proteins; C098669:TOB1 protein, human; C490903:Tob1 protein, mouse; D025521:Tumor Suppressor Proteins; C070114:BTG2 protein, human