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. 1999 May;152(1):221–235. doi: 10.1093/genetics/152.1.221

lir-2, lir-1 and lin-26 encode a new class of zinc-finger proteins and are organized in two overlapping operons both in Caenorhabditis elegans and in Caenorhabditis briggsae.

P Dufourcq 1, P Chanal 1, S Vicaire 1, E Camut 1, S Quintin 1, B G den Boer 1, J M Bosher 1, M Labouesse 1
PMCID: PMC1460593  PMID: 10224256

Abstract

lin-26, which encodes a unique Zn-finger protein, is required for differentiation of nonneuronal ectodermal cells in Caenorhabditis elegans. Here, we show that the two genes located immediately upstream of lin-26 encode LIN-26-like Zn-finger proteins; hence their names are lir-1 and lir-2 (lin-26 related). lir-2, lir-1, and lin-26 generate several isoforms by alternative splicing and/or trans-splicing at different positions. On the basis of their trans-splicing pattern, their intergenic distances, and their expression, we suggest that lir-2, lir-1, and lin-26 form two overlapping transcriptional operons. The first operon, which is expressed in virtually all cells, includes lir-2 and long lir-1 isoforms. The second operon, which is expressed in the nonneuronal ectoderm, includes short lir-1 isoforms, starting at exon 2 and lin-26. This unusual genomic organization has been conserved in C. briggsae, as shown by cloning the C. briggsae lir-2, lir-1, and lin-26 homologs. Particularly striking is the sequence conservation throughout the first lir-1 intron, which is very long in both species. Structural conservation is functionally meaningful as C. briggsae lin-26 is also expressed in the nonneuronal ectoderm and can complement a C. elegans lin-26 null mutation.

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