Proviral genome of radiation leukemia virus: Molecular cloning of biologically active proviral DNA and nucleotide sequence of its long terminal repeat

The proviral genome of a leukemogenic and thymotropic C57BL/Ka mouse retrovirus, RadLV/VL₃(T+L+), was cloned as a biologically active PstI insert in the bacterial plasmid pBR322. Its restriction map was compared with those, already known, of two nonthymotropic and nonleukemogenic viruses of the same mouse strain: the ecotropic BL/Ka(B) virus and the xenotropic constituent of the radiation leukemia virus complex. Differences were observed around the gag-pol gene junction, in the pol gene, and in the env gene. Moreover, the nucleotide sequence of the RadLV/VL₃(T+L+) long terminal repeat revealed the existence of two copies of a 43-base-pair sequence, of which BL/Ka(B) possesses only one copy.