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I am reading this paper, which shows that a Human Endogenous Retrovirus (HERV) K provirus is present at the orthologous position of gorilla and chimpanzee genomes but absent in the human genome.

If it's not present in the human genome, why is it still called a HERV? Should it not just be an endogenous retrovirus?

(I am not a biology student, so I might not have understood the idea of a provirus/retrovirus entirely.)

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First of all, the HERV-K virus is present in the human genome, in fact it is one of the most common endogenous retroviruses there (see references 1 and 2).

In a viral infection, these proviruses get integrated into the human genome and can be found later there. This is a useful tool when you want to find out details about the split of closely related species like the great apes and humans. If you find such a provirus in all analyzed species, the integration must have happened latest at the last common ancestor. If it is only found in a part of them, it happened after the species divided. The figure (from reference 3) shows this shematically:

enter image description here

The authors of "your" article did this and found the integration of the retrovirus in a specific locus in the genome of gorilla, chimpanzee and human and found it only in the first two. From this they conclude that the apes are closer related to each other than to the human.

So in summary it means that the HERV-K is not present at one specific site of the human genome, not in general.

References:

  1. HERV-K: the biologically most active human endogenous retrovirus family.
  2. HERV-K(HML-2), the Best Preserved Family of HERVs: Endogenization, Expression, and Implications in Health and Disease
  3. Differences in HERV-K LTR insertions in orthologous loci of humans and great apes.
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