Abstract
By screening for marker-cassette deletion mutants of a murine leukaemia virus-based replication-competent vector, two occurrences of tRNA sequence patch insertions were identified. In one of the cases, 28 nucleotides from the 5' end of tRNALys4 were inserted in the plus-strand orientation, which points to a novel strand-transfer mechanism to tRNAs during reverse transcriptase-mediated retroviral recombination.