CELE_C05G5.6, CELE_C05G5.6.2, CELE_C05G5.6.3, CELE_C05G5.6.1, C05G5.6

let-7 encodes a 21-nucleotide microRNA (also known as a small temporal RNA, or stRNA) that is conserved in bilateral animal species (including vertebrates, ascidians, hemichordates, molluscs, annelids and arthropods), but is not found in cnidarians, poriferans, fungi, plants, protists, archaea, or bacteria; let-7 is required for the transition from late larval to adult cell fates, and for larval viability; like lin-4, let-7 is complementary to sequences in the 3' untranslated regions of target genes that it negatively regulates; let-7 RNA expression is first detected at late larval stages and is negatively regulated by the product of one of its targets, hbl-1, in a negative feedback loop; the temporal regulatory element (TRE), situated about 1200 base pairs upstream of the start of the mature let-7 RNA, is both necessary and sufficient for temporal upregulation of let-7 transcription; DCR-1, ALG-1, and ALG-2 are required for the maturation and activity of let-7 stRNA; since let-7 homologs are expressed in zebrafish embryos and in adult annelids and molluscs, let-7 may have a conserved function in heterochronic developmental regulation in bilateria.

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