Operons in worms

Operons contain multiple adjacent genes whose transcription is regulated by the transcription of a single polycistronic message. The processing of polycistronic pre-mRNA involves 3' end formation and trans-splicing by the specialized SL2 small nuclear ribonucleoprotein particle. In the June 20 Nature, Blumenthal et al. describe a screen for SL2-containing mRNAs in the Caenorhabditis elegans genome (Nature 2002, 417:851-854). They used a probe enriched for SL2-containing mRNA to hybridize to microarrays containing over 17,000 genes. They selected around 1,200 genes, including many genes with known SL2-containing mRNAs. Most of these genes (86%) are located downstream in operons, indicating a strong correlation between SL2 trans-splicing and downstream location in an operon. Blumenthal et al. estimated that the C. elegansgenome may contain as many as 1,068 operons, representing over 2,600 genes (or up to 15% of genes).