Figure 4

Phylogenetic analysis of XMRV. All full-length XMRV sequences available in GenBank (accessed on April 28, 2010) were aligned using ClustalW. Unrooted (panel A) and rooted (panel B) phylogenetic trees were generated using the neighbor-joining algorithm of MEGA 4.0 [67] with default settings. Scale bars indicate evolutionary distance in base substitutions per site (i.e., the distance shown in panel A equals 2 substitutions per 10,000 bases). Note that after the original sequencing of XMRV strains VP62, VP42 and VP35 [3], strain VP62 was resequenced ("VP62 corrected"; [11]). The resulting sequence reveals a closer similarity between VP62 and other XMRV strains and suggests that the branch lengths of VP35 and VP42 are also likely overestimated due to PCR or sequencing errors. mChrom13 indicates an endogenous MLV sequence located on Mus musculus chromosome 13 [GenBank: CT030655.7], and is the most closely related non-XMRV sequence found by BLAST search of GenBank using the XMRV_22Rv1 sequence. DG-75 indicates DG-75 MLV [GenBank: AF221065].