RESUMEN
To investigate the molecular mechanisms of the oncogenic effects of avian leukosis virus subgroup J (ALV-J), we examined mutations in and the expression of p53 in the myelocytomas distributed in the liver, spleen, trachea, and bone marrow, as well as in fibrosarcomas in the abdominal cavity and hemangiomas in skin from chickens that were naturally or experimentally infected with ALV-J. Two types of mutations in the p53 gene were detected in myelocytomas of both the experimentally infected and the naturally infected chickens and included point mutations and deletions. Two of the point mutations have not been reported previously. Partial complementary DNA clones with a 122-bp deletion in the p53 gene ORF and a 15-bp deletion in the C-terminus were identified in the myelocytomas. In addition, moderate expression of the mutant p53 protein was detected in the myelocytomas that were distributed in the liver, trachea, spleen, and bone marrow. Mutant p53 protein was not detected in the subcutaneous hemangiomas or in the abdominal fibrosarcomas associated with natural and experimental ALV-J infection, respectively. These results identify mutations associated with abnormal expression of p53 in ALV-J-associated myelocytomas, suggesting a role in tumorigenesis.