Retroviral determinants of leukemogenesis.

The slowly transforming, leukemogenic retroviruses of humans and other mammals induce malignant disease after prolonged latency but lack an oncogene to which their malignant potential can be attributed directly. The leukemogenic activity of these retroviruses can be attributed to at least three factors, including (1) transcriptional regulatory sequences in the long terminal repeat: (2) the insertional mutagenesis of cellular protooncogenes, thus activating their malignant potential; and (3) the actions of structural and regulatory proteins encoded by viral genes. The goal of this review is to summarize recent findings regarding the roles of these factors in retroviral leukemogenesis. The focus of the review is on the slowly transforming, leukemogenic retroviruses of mammals, including humans and experimental animals.