Capsid protein Reverse Transcriptase Envelope Protein / Nonacute retrovirus R US gag pol env U3 R Genome of virus that can infect but not transform cell Cellular proto-oncogene in infected cell c-onc c-onc Acute transforming retrovirus Transfer of gene from host cell R US gag pol env v-onc U3 R to viral genome allows virus to infect and transform cell V-onc Mutation creates oncogene