Generation of AKR mink cell focus-forming virus: nucleotide sequence of the 3' end of a somatically acquired AKR-MCF.

The 3' end of an AKR-MCF provirus (MCFr35) was cloned and found to be biologically active. Comparison of the nucleotide sequence of MCFr35 with the sequence of other MuLVs revealed that the MCFr35 was most likely derived from the same xenotropic and ecotropic parents, which were involved in the generation of AKR-MCF247. Ecotropic sequences are present around the XbaI site at position 7.9 on the genomic map, and in the long terminal repeat. Most of the T1 oligonucleotide sequences, characteristic for the leukemogenic "class I" MCFs, are also present in MCFr35, with the exception of T1 oligonucleotides 108 and 18. The MCFr35 LTR contains a duplicated enhancer sequence from a xenotropic-like provirus, which is present only once per haploid genome equivalent. The 3' end of MCFr35 consist predominantly of nonecotropic sequences, thereby delimiting the positions of recombination in various MCF viruses.