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.
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.
Dufourcq
P
P
IGBMC, CNRS/INSERM/ULP, 67404 Illkirch Cedex, France.
Chanal
P
P
Vicaire
S
S
Camut
E
E
Quintin
S
S
den Boer
B G
BG
Bosher
J M
JM
Labouesse
M
M
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D002107:Caenorhabditis / Q000235:genetics*; D017173:Caenorhabditis elegans / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins / Q000235:genetics*; D017931:DNA Primers; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000378:metabolism; D017930:Genes, Reporter; D005816:Genetic Complementation Test; D017403:In Situ Hybridization; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics*; D016335:Zinc Fingers
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C119886:LIR-1 protein, C elegans; C119887:LIR-2 protein, C elegans; D009687:Nuclear Proteins; D014157:Transcription Factors; C090507:lin-26 protein, C elegans