Isolation and phylogeny of new endogenous retroviral sequences belonging to the HERV-F family

Expression analysis of endogenous retroviral elements belonging to the HERV-F family from human tissues and cancer cells

Based on the primer binding site for Phe-tRNA, human endogenous retroviruses (HERVs) have been classified as HERV-F family members, HERV-F, HERV-FXA, HERV-Fb, and HERV-Fc. The HERV-F family was expressed in human placenta preferentially. We investigated pol fragments of HERV-F family in various human tissues and cancer cells. The pol gene was expressed in human placenta only among tissues (brain, prostate, testis, heart, kidney, liver, lung, placenta, skeletal muscle, spleen, thymus, uterus), but detected in various cancer cell lines (RT4, BT-474, HCT-116, TE-1, UO-31, Jurkat, A549, MCF7, OVCAR-3, MIA-PaCa-2, PC3, LOX-IMVI, AZ521, 2F7, U-937, and C-33A) except for PFSK-1 and HepG2 by RT-PCR analysis. Expression and sequencing data of the 37 clones imply that the pol gene of HERV-F family is active in cancer cells, which may have potential role related to cancer development.

The evolution, distribution and diversity of endogenous retroviruses

The retroviral capacity for integration into the host genome can give rise to endogenous retroviruses (ERVs): retroviral sequences that are transmitted vertically as part of the host germ line, within which they may continue to replicate and evolve. ERVs represent both a unique archive of ancient viral sequence information and a dynamic component of host genomes. As such they hold great potential as informative markers for studies of both virus evolution and host genome evolution. Numerous novel ERVs have been described in recent years, particularly as genome sequencing projects have advanced. This review discusses the evolution of ERV lineages, considering the processes by which ERV distribution and diversity is generated. The diversity of ERVs isolated so far is summarised in terms of both their distribution across host taxa, and their relationships to recognised retroviral genera. Finally the relevance of ERVs to studies of genome evolution, host disease and viral ecology is considered, and recent findings discussed.