Nat. Struct. Mol. Biol. 15, 581–590 (2008); published online 25 May 2008; corrected after print 18 June 2008

In the version of this article initially published, the Abstract did not convey that two conclusions regarding cis-NATs, presented in Table 1, were derived from analysis of previously published data (references 20 and 21 in the paper). The third sentence of the Abstract should read: “First, >100 cis-NATs with overlapping 3′ exons generate 21-nt and, based on previously published small RNA data, Dicer-2 (Dcr-2)–dependent, 3′-end modified siRNAs.” The correction has been made to the HTML and PDF versions of the article.