Global analysis of Caenorhabditis elegans operons

Caenorhabditis elegans and its relatives are unique among animals, possibly even among eukaryotes, in having operons. In these regulated multigene transcription units, a polycistronic pre-mRNA is processed to monocistronic mRNAs by 3' end formation and trans-splicing utilizing a special snRNP, the SL2 snRNP, for downstream mRNAs1. Previously, the correlation between downstream location in an operon and SL2 trans-splicing has been strong, but anecdotal. Although only 28 operons have been reported previously, the complete sequence of the genome reveals numerous gene clusters. To determine how many represent operons, we probed full-genome microarrays for SL2-containing mRNAs. We found significant enrichment for about 1200 genes including most of a group of several hundred genes represented by cDNAs that contain SL2 sequence. Analysis of their genomic arrangements indicates that >90% are downstream genes, falling in 790 distinct operons. We conclude that the genome contains at least 1000 operons, 2- 8 genes in length, that contain ~15% of C. elegans genes. Most of the operons have not been reported previously, and numerous examples of co-transcription of genes encoding functionally related proteins are evident. Inspection of the operon list should reveal heretofore unknown functional relationships. Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Keywords: Logical Set Computed