Cross-Species Transmission and Differential Fate of an Endogenous Retrovirus in Three Mammal Lineages
(a) Age distribution of proviral insertions inferred from LTR-LTR divergence. The y axis shows the number of insertions for each age class binned in MY on the x axis. Each ERV family is shown as bars of different colors. (b) Evidence of ‘gene’ conversion between 5’ and 3’ LTR of the same provirus. Four LTR trees are shown for four pairs of orthologous proviruses shared by M. lucifugus (MLERV) and M. brandtii (MBERV). Each maximum likelihood tree was built from a multiple alignment of the 5’ and 3’ LTRs from each provirus rooted with a non-orthologous LTR from M. lucifugus (also illustrated in S2 Fig). The support for each node as determined with an approximate likelihood ratio test (aLRT) is shown. The fact that 5’ and 3’ LTR from the same provirus tend to group together rather than by species is indicative of gene conversion between the LTRs along the two species lineages following proviral insertion in their common ancestor.