Regulation of the Caenorhabditis elegans posterior hox gene egl ‐ 5 by microRNA and the polycomb‐like gene sop ‐ 2

In Caenorhabditis elegans , the domains of Hox gene expression are controlled by the novel global regulatory gene sop ‐ 2 . We identified a region located 3′ of the Hox gene egl ‐ 5 that promotes ectopic expression of an egl ‐ 5 reporter gene in a sop ‐ 2 mutant. SOP‐2 could directly block positive regulatory factors acting in this region, or it could block their expression. We identified three possible miRNA binding sites within the egl ‐ 5 3′ untranslated region (UTR). Cognate microRNAs are expressed in relevant tissues and can block egl ‐ 5 expression when expressed from a transgene. Mutation of the putative binding sites in the egl ‐ 5 3′UTR resulted in a modest degree of misexpression of a minimal egl ‐ 5 reporter gene, suggesting that microRNAs may contribute to the tight restriction of egl ‐ 5 expression to particular cell lineages. Developmental Dynamics 238:595–603, 2009. © 2009 Wiley‐Liss, Inc.