[Retroviral oncogenes and their cellular proto-oncogenes].

Recent data on the genome structure of transforming retroviruses and their cellular counterparts has been reviewed. Retroviruses are divided in several groups according to their oncogenic potential. Comparison of oncogenes and their protein products for most abundant transforming viruses are presented. Probable mechanisms of capture of cellular proto-oncogenes by retroviruses and the hypothesis of existence of endogenous transforming viruses are discussed. General features of cellular proto-oncogenes and possible ways of their activation resulting in neoplastic transformation are discussed. Some unresolved problems of retroviral carcinogenesis, in particular, the problem of existence of unidentified "X"-genes in retroviral genomes and involvement of constitutional viral genes in carcinogenesis are mentioned.