officially released October 8, 2009, associates an endogenous retrovirus
with CFS. The press release notes that this type of virus can activate or
possibly reactivate other viruses. What was not mentioned was the possible
DNA / genetic connection.
An Endogenous Retrovirus (ERV) is a viral sequence that has become part of
the infected "animal's" genome. Upon entering a cell, a retrovirus copies
its RNA genome into DNA, and inserts the DNA copy into one of the host
cell's chromosomes. Different retroviruses target different species and
types of host cells; the retrovirus only becomes endogenous if it inserts
into a cell whose chromosomes will be inherited by the next generation, i.e.
an ovum or sperm cell. The offspring of the infected individual will have a
copy of the ERV in the same place in the same chromosome in every single one
of their cells.
This happens more often than you might think; 8% of the modern human
genome<http://www.nature.com/nature/journal/v409/n6822/abs/409860a0.html;jsessionid=6A41697D465447C57E986AAA7FB8C63B>
is
derived from ERVs. Repeated sequences of this kind were formerly considered
to be non-functional, or "junk" DNA. However, scientists are gradually
finding more and more examples of viral sequences that appear to have some
kind of function in human cells. For example, many ERV sequences play a role
in human gene regulation. ERVs contain viral genes, and also sequences -
known as promoters - that dictate when those genes should be switched on.
When an ERV inserts into the host's chromosome, its promoter can start to
interfere with the regulation of any nearby human genes.
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