horizontal gene transfer: viral DNA (Introduction)

by David Turell , Friday, December 19, 2014, 15:07 (3406 days ago) @ David Turell

Mice carry endogenous retroviral DNA from previous ancestors to help build antibodies when necessary;-http://www.the-scientist.com//?articles.view/articleNo/41707/title/Repurposed-Retroviruses/-"Retroviral sequences in mammalian genomes are the remnants of old viral infections and, for the most part, their expression is suppressed. But a report published today (December 18) in Science suggests that, in B cells, a particular type of antigen can stimulate transcription of these viral relics, which in turn prompts cell proliferation and antibody production.-"The work is a “tour de force,” said Michael Cancro, a professor of pathology and laboratory medicine at the University of Pennsylvania Perelman School of Medicine who was not involved in the study. “It may well be the seminal paper in resolving this long-standing conundrum of exactly what is a TI-2 antigen doing to get these B cells to kick off.”-"TI-2 antigens are so named because they can stimulate B cells to produce antibodies in a T cell-independent (TI) manner. Unlike protein antigens—which need T helper cells to interact with and stimulate the B cell in which they are being processed—TI antigens can stimulate B cells on their own. TI-2 antigens tend to be large polysaccharides with repetitive structures, such as those that encapsulate certain bacteria and viruses. It is known that they interact via multiple crosslinks with B cell receptors, but the subsequent pathway to antibody production was a mystery.-"It turned out that TI-2 stimulated B cells to produce a wide range of endogenous retrovirus (ERV) RNA transcripts from across the genome. These transcripts were then also reverse-transcribed into DNA. Indeed, the team showed that treating the mice with drugs that inhibit reverse transciptase not only reduced ERV-derived DNA, but also the production of TI-2-induced antibodies."