Coexpression of mutant p53 and p193 renders embryonic stem cell-derived cardiomyocytes responsive to the growth-promoting activities of adenoviral E1A.
Expression of adenoviral E1A in cardiomyocytes results in the activation of DNA synthesis followed by apoptosis. In contrast, expression of simian virus 40 large T antigen induces sustained cardiomyocyte proliferation. Previous studies have shown that T antigen binds to 2 proapoptotic proteins in cardiomyocytes, namely the p53 tumor suppressor and p193 (a new member of the BH3-only proapoptosis subfamily). Structure-function analyses identified a p193 C-terminal truncation mutant that encodes prosurvival activity. This mutant was used to test the role of p193 in E1A-induced cardiomyocyte apoptosis. E1A induced apoptosis in cardiomyocytes derived from differentiating embryonic stem cells. Expression of the prosurvival p193 mutant alone or a mutant p53 alone did not block E1A-induced apoptosis. In contrast, combinatorial expression of mutant p193 and mutant p53 blocked E1A-induced apoptosis, resulting in a proliferative response indistinguishable from that seen with T antigen. These results confirm the hypothesis that there are 2 proapoptotic pathways, encoded by p53 and p193, respectively, which restrict cardiomyocyte cell cycle activity in differentiating embryonic stem cell cultures. Furthermore, these results explain in molecular terms the phenotypic differences of E1A versus T-antigen gene transfer in cardiomyocytes.
Pasumarthi
K B
KB
Wells Center for Pediatric Research and Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, IN, USA.
Tsai
S C
SC
Field
L J
LJ
D016475:3T3 Cells; D017500:Adenovirus E1A Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D000957:Antigens, Viral, Tumor / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003114:Colony-Forming Units Assay; D018014:Gene Transfer Techniques; D051379:Mice; D009154:Mutation; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D012038:Regeneration; D050720:Retinoblastoma-Like Protein p107; D015398:Signal Transduction / Q000502:physiology; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D013329:Structure-Activity Relationship; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology
D017500:Adenovirus E1A Proteins; D000957:Antigens, Viral, Tumor; D051023:BH3 Interacting Domain Death Agonist Protein; C494815:Bid protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C489485:Rbl1 protein, mouse; D050720:Retinoblastoma-Like Protein p107; D016159:Tumor Suppressor Protein p53