Functional abrogation of p53 is required for T-Ag induced proliferation incardiomyocytes

N. E. HUH, K. B. S. PASUMARTHI, M. H. SOONPAA, S. JING, B. PATTON AND L. J. FIELD. Functional Abrogation of p53 is Required for T-Ag Induced Prolifera tion in Cardiomyocytes. Journal of Molecular and Cellular Cardiology (2001) 33, 1485-1413. Targeted expression of the SV40 large T-antigren oncoprotei n (T-Ag) induces cardiomyocyte proliferation in the atria and ventricles of transgenic mice, Previous studies have identified the p53 tumor suppressor , p107 (a homologue of the retinoblastoma tumor suppressor), and p193 (a no vel BH3 only proapoptosis protein) as prominent T-Ag binding proteins in ca rdiomyocyte cell lines derived from these transgenic mice. To further explo re the significance of these protein-protein interactions in the regulation of cardiomyocyte proliferation, a transgene comprising the human atrial na triuretic factor (ANF) promoter and sequences encoding a mutant T-Ag lackin g the p53 binding domain was generated. Repeated micro-injection of this DN A gave rise to genetically mosaic animals with minimal transgene content, s uggesting that widespread cardiac expression of mutant T-Ag was deleterious . This notion was supported by the observation that the transgene was selec tively lost from the cardiac myocytes (but not the cardiac fibroblasts) in the mosaic animals. Crosses between the mosaic mice and animals expressing a cardiac restricted dominant negative p53 resulted in transgene transmissi on with ensuing overt cardiac tumorigenesis, Transfection of the mutant T-A g in embryonic stem (ES) cell-derived cardiomyocytes resulted in wide-sprea d cell death with Characteristics typical of apoptosis, Co-transfection wit h a dominant negative p53 transgene rescued mutant T-Ag-induced cell death in the ES-derived cardiomyocyte cultures, resulting in a marked proliferati ve response similar to that seen in vivo with the rescued transgenic mouse study, These results indicate that T-Ag expression in the absence of p53 fu nctional abrogation results in cardiomyocyte death. (C) 2001 Academic Press .