Figure 1.

Retroviral envelope protein-based phylogenic tree with positions of the identified rabbit Env-Ory1- and Env-Ory2, and of the human and mouse syncytins. The tree was determined by the neighbor-joining method using envelope TM subunit sequences (see ref [12]) from murine and human ERVs, and infectious retroviruses. The horizontal branch length and the scale indicate the percentage of amino acid substitutions from the node. Percent bootstrap values obtained from 1,000 replicates are indicated.