Excision of the DBA ecotropic provirus in dilute coat-color revertants of mice occurs by homologous recombination involving the viral LTRs.

The dilute (d) coat color mutation of DBA/2J mice is closely associated with the site of integration of an ecotropic murine leukemia provirus. In five independent dilute revertants (d+) examined, reversion to wild-type coat-color correlated with the loss of most of the ecotropic proviral genome, indicating that virus integration caused the mutation. Molecular cloning and restriction enzyme analysis of the viral preintegration site as well as two independent dilute revertants, showed that exactly one long terminal repeat (LTR) remained in each revertant DNA, suggesting that virus excision occurred by homologous recombination involving the viral LTRs.