RETROTRANSPOSITION OF NONVIRAL RNAS IN AN AVIAN PACKAGING CELL-LINE

Retroviruses produced from the quail packaging cell line SE21Q1b predo minantly contain cellular RNAs instead of viral RNAs. These RNAs can b e reverse transcribed and integrated into the genomes of newly infecte d cells and are thereafter referred to as newly formed retrogenes. We investigated whether retrogene formation can occur within SE21Q1b cell s themselves and whether this occurs intracellularly or via extracellu lar reinfection. By using packaging cell line mutants derived from the SE21Q1b provirus and selectable reporter constructs, we found that th e process requires envelope glycoproteins and a retroviral packaging s ignal. Our results suggest that extracellular reinfection is the prima ry route of retrotransposition of nonviral RNAs.