Argonaute 2 (Ago2) is unique among its family: It is the only one of the four mammalian Argonaute proteins that exhibits endonuclease “slicer” activity (facilitation of miRNA-guided cleavage of target mRNA).
However, as Drs. Donal O’Carroll and Alexander Tarakhovsky (The Rockefeller Institute) report, Ago2’s defining characteristic is surprisingly non-essential for its role in hematopoiesis and miRNA biogenesis.
Drs. O’Carroll, Tarakhovsky and colleagues generated transgenic mice harboring mutated versions of Ago2 in their bone marrow. The researchers found that Ago2 is, indeed, quite necessary for normal blood cell development. Its endonulcease activity, however, is not.