The indications of tRF repression evasion, together with the observation that recent Cer-SERV-1 proviruses show evidence of evolving binding motifs for embryonic stem cell-specific transcription factors, such as FoxD3 and FoxJ2, it appears that SERV is further adapting from exogenous infections to a lifestyle that specializes in (re-)infection of the embryonic germ line. Here, CBLN1 is linked to infection.