Transcriptional regulation of Sox2 by the retinoblastoma family of pocket proteins
Vilas, J. M.; Ferreiros, A.; Carneiro, C.; Morey, L.; Silva-alvarez, S. D.; Fernandes, T.; Abad, M.; Croce, L. D.; Garcia-Caballero, T.; Serrano, M.; Rivas, C.; Vidal, A.; Collado, M.Vilas Martínez, Jessica María; Ferreirós López, Alba; Carneiro Freire, Carmen; Morey, Lluis; Da Silva Álvarez, Sabela; Fernandes, Tania; Abad, María; Di Croce, Luciano; García Caballero, Tomás; Serrano, Manuel; Rivas, Carmen; Vidal, Anxo; Collado Rodríguez, Manuel
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MeSHAnimals | Cellular Reprogramming | Epigenesis, Genetic | Gene Expression Regulation, Developmental | Gene Expression Regulation, Neoplastic | Genotype | HEK293 Cells | Humans | Induced Pluripotent Stem Cells | Mice, 129 Strain | Mice, Inbred C57BL | Mice, Knockout | Neoplastic Stem Cells | Phenotype | Pituitary Neoplasms | RNA Interference | Retinoblastoma Protein | Retinoblastoma-Like Protein p107 | Retinoblastoma-Like Protein p130 | SOXB1 Transcription Factors | Transcription, Genetic | Transfection | Tumor Suppressor Protein p53
Cellular reprogramming to iPSCs has uncovered unsuspected links between tumor suppressors and pluripotency factors. Using this system, it was possible to identify tumor suppressor p27 as a repressor of Sox2 during differentiation. This led to the demonstration that defects in the repression of Sox2 can contribute to tumor development. The members of the retinoblastoma family of pocket proteins, pRb, p107 and p130, are negative regulators of the cell cycle with tumor suppressor activity and with roles in differentiation. In this work we studied the relative contribution of the retinoblastoma family members to the regulation of Sox2 expression. We found that deletion of Rb or p130 leads to impaired repression of Sox2, a deffect amplified by inactivation of p53. We also identified binding of pRb and p130 to an enhancer with crucial regulatory activity on Sox2 expression. Using cellular reprogramming we tested the impact of the defective repression of Sox2 and confirmed that Rb deficiency allows the generation of iPSCs in the absence of exogenous Sox2. Finally, partial depletion of Sox2 positive cells reduced the pituitary tumor development initiated by Rb loss in vivo. In summary, our results show that Sox2 repression by pRb is a relevant mechanism of tumor suppression.