Three New Types of Viral Oncogenes in Defective Avian Leukemia Viruses. I. Specific Nucleotide Sequences of Cellular Origin Correlate with Specific Transformation

Abstract

On the basis of their oncogenic properties, avian retroviruses can be assigned to either of two major classes. Of many characterized natural field isolates, the vast majority (nondefective avian leukemia viruses [ALVs]) are weakly oncogenic and cause predominantly lymphatic leukemia after a prolonged latency period of months to years following inoculation of susceptible strains of chickens. ALVs most frequently occur as independent agents and contain all the genetic information required for viral replication. In contrast, several other avian retroviruses are highly oncogenic and produce disease after a short latency period of days to weeks. These highly oncogenic viruses include the replication-competent avian sarcoma viruses (ASVs) (or Rous viruses), which readily induce sarcomas in susceptible birds and transform fibroblasts in vitro, and the replication-defective leukemia viruses (DLVs), which require helper ALVs for their propagation in cultured cells (for review, see Graf and Beug 1978).