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Operons and SL2 trans-splicing exist in nematodes outside the genus Caenorhabditis
D Evans1, D Zorio, M MacMorris
1Department of Biology, Indiana University, Bloomington, IN 47405, USA.
Summary
Nematode genomes can contain gene clusters, similar to bacterial operons, where multiple genes are transcribed from one promoter. This organization, found in Dolichorhabditis, suggests operons predate the split within the Rhabditidae family.
Area of Science:
- Genomics
- Molecular Biology
- Evolutionary Biology
Background:
- Most eukaryotic genomes arrange genes individually on chromosomes.
- The nematode Caenorhabditis elegans exhibits unique polycistronic gene clusters, akin to bacterial operons.
- These clusters are transcribed from a single promoter, with subsequent processing into individual mRNAs.
Purpose of the Study:
- To investigate the presence of operon-like gene organization in other nematode species.
- To determine if this gene arrangement is unique to Caenorhabditis elegans or more widespread.
- To understand the evolutionary history of gene organization in nematodes.
Main Methods:
- Identification of spliced leader (SL) RNAs (SL1 and SL2) in Dolichorhabditis.
- Sequencing of a Dolichorhabditis genomic region containing a gene cluster.
- Analysis of gene transcription and processing, including trans-splicing.
Main Results:
- Both SL1 and SL2 RNAs were detected in the nematode Dolichorhabditis.
- A Dolichorhabditis gene cluster with operon-like characteristics was identified.
- The downstream gene in the cluster was shown to be trans-spliced to SL2.
Conclusions:
- The operon-like gene organization is present in Dolichorhabditis, a distantly related nematode.
- This gene arrangement predates the divergence of Caenorhabditis and other Rhabditidae genera.
- Operon-like structures in animal genomes may be more common than previously thought.