Mammalian microRNAs predominantly act to decrease target mRNA levels ; P' {* i7 C( x q! z7 GNature 466, 835-840 (12 August 2010) | doi:10.1038/nature09267; Received 16 February 2010; Accepted 2 June 2010 1 r3 i2 l' T2 d% h) T. r7 zhttp://www.nature.com/nature/jou ... pdf/nature09267.pdf