A class II retrotransposon belonging to the MERV-K family was inserted into intron 1. Sequence analysis demonstrated the MERV element contained two LTRs that were 317 bp in length and an EcoRI site 655 bp from the 3' end. This BALB/cJ specific sequence has been deposited in NCBI as EU233786. Northern blot detected chimeric transcripts from these animals.