HIV-1 elicits RNA silencing in human cells, but it also contains a sequence that suppresses the process, according to researchers at the National Institute of Allergy and Infectious Diseases. "Nucleic acid-based immunity in mammalian cells has been found before, but to date, there has been no single report of a natural small interfering RNA [siRNA] that is triggered by HIV in human cells," says coauthor Kuan-Teh Jeang. He adds that the virus' "counter strategy" is also unprecedented.
Jeang, Yamina Bennasser, and colleagues characterized a sequence in the HIV-1 genome that encodes a rare siRNA precursor: a short hairpin RNA (shRNA) that is processed by the Dicer (or by a Dicer-like) ribonuclease into siRNAs. In addition, they found that the virus prevents RNA silencing through a suppressor present in its Tat protein, which interferes with Dicer's activity.
"It's ... a very intriguing story," says Mario Stevenson of the University of Massachusetts....
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