The HERV-K Family of Human Endogenous Retroviruses

B Berkhout


Of the numerous endogenous retroviral elements that are present

in the human genome, the abundant HERV-K family is distinct because several

members are transcriptionally active and coding for biologically active

proteins.  The HERV-K genome has been demonstrated to encode an active

dUTPase, protease, and endonuclease, and we now report the cloning of a

partially active RT enzyme.  Inspection of the HERV-K sequences revealed

signs of recombination, a hallmark of exogenous retroviruses. Other genome

characteristics that were reported previously for actively replicating

retroviruses are also apparent for the endogenous HERV-K virus.  In

particular, we observed suppression of the dinucleotide CpG that represents

potential methylation sites.  We also were able to evaluate the mutational

spectrum of the HERV-K Reverse Transcriptase (RT) enzyme by comparison of 34

available sequences. Interestingly, this analysis revealed a striking similarity

with the properties of the HIV-1 RT enzyme, with a preference for G-to-A

transitions, which may explain the abundance of the A-nucleotide in the

retroviral genome of HIV-1 and HERV-K