e
system's 'a la carte' process happens is still murky," says Craig.
But the a la carte approach provides great diversity from a limited
number of choices, whether in the immune system or in a cafeteria. For
example, at a cafeteria, one diner could have a meal of mashed
potatoes, broccoli and a pork chop, and another French fries, salad and
a hamburger, and so on through all the possible combinations of
offerings.
While the choices aren't as tasty, immune cells select sections of
certain genetic instructions in order to make instructions for a
protein that will recognize a particular antigen. Machinery snips out
unwanted genetic sections and reconnects the leftover ones, creating a
unique gene (the cellular equivalent of the diner's meal). Snipping out
different sections will lead to a different gene, carrying instructions
for a different protein that will recognize a different antigen, and on
and on.
This a la carte process, known as V(D)J recombination, is similar to
the excision of jumping genes, but none had matched one of its
characteristic oddities: As the unwanted DNA is being removed, the
remaining DNA forms a tiny loop.
Unexpectedly, when Hermes is being cut out of the DNA, the leftover DNA
also forms a hairpin loop, temporarily doubling back on itself,
postdoctoral fellows Liqin Zhou, Ph.D., and Rupak Mitra, Ph.D.,
discovered in experiments in test tubes and with E. coli bacteria.
Although this loop distances Hermes from its well-studied cousins, the
Hermes protein still has an important family trait, the researchers
report. Colleagues at the National Institutes of Health found that a
few key building blocks in the protein's DNA-snipping crevice are
identical to those in other jumping genes' proteins, even though the
overall sequence is quite different.
"Because of its similarities both to V(D)J recombination and to other
families of jumping genes, Hermes is the first real link between the
two processes," says Craig. "It also is likely to be a good model t
'"/>Source:
Page: 1 2 3 Related biology news :1.
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