ScienceDaily (May 3, 2010) — MicroRNAs are small bits of RNA within cells that wield enormous power. They influence virtually every biological process by controlling the "expression" of genes. Helping them in exerting this control is a unique class of proteins called Argonautes.
Micro RNA Biogenesis
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Source/Fonte: OpenByosystems
Cold Spring Harbor Laboratory (CSHL) researchers led by Professor and HHMI investigator Gregory Hannon, Ph.D, now report that in animal cells, one of Argonautes, called Ago2, has a different role -- it helps generate microRNAs instead. The study, which appears online, ahead of print in Nature on April 27th points to an alternative pathway of microRNA generation that the team discovered by analyzing a microRNA molecule produced in developing red blood cells.
In 2004, a team led by Hannon and Leemor Joshua-Tor, another CSHL Professor discovered that Ago2 functions as a slicer enzyme that chops up its targets -- messenger RNAs encoded by genes -- by using small RNA molecules (for example, microRNAs) as guides to home in on the correct messenger RNAs. The team's subsequent studies revealed a possible role for this slicing, or catalytic, activity of Ago2 in mammalian oocytes.
"But we found that although Ago2 is critical for the viability of embryos during development in mice, Ago2's microRNA partners generally undertake gene regulation during embryogenesis in ways that do not require the catalytic activity of this enzyme" explains Hannon. "So the basis of the evolutionary pressure to retain this catalytic ability was a mystery to us."
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Sihem Cheloufi Camila O. Dos Santos Mark M. W. Chong & Gregory J. Hannon
Nature nfv, (2010) | doi:10.1038/nature09092.
