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Caenorhabditis elegans operons: form and function

Nature Reviews Genetics volume 4, pages 110–118 (2003)Cite this article

Key Points

  • C. elegans is unusual among animals in having operons. These contain co-transcribed genes that make a polycistronic pre-mRNA that is subsequently separated into single-gene mRNAs by 3′-end formation and trans-splicing.

  • Approximately 15% of C. elegans genes are encoded in operons that contain 2–8 genes.

  • Operon-like multigene assemblies are also found in other nematodes and in other species that process their pre-mRNAs using spliced-leader-type trans-splicing.

  • Operons sometimes co-regulate genes that make proteins with related functions. The study of genes that are co-transcribed in C. elegans operons might be a useful tool to identify the proteins that are functionally related to a particular gene of interest.

  • Some functional classes of gene are preferentially included in operons, whereas others are excluded or rarely included.

  • Genes that encode the proteins that function in RNA degradation are the class most frequently included in operons. Other frequently included groups include all of the genes that encode the basic machinery of transcription, RNA splicing and translation, as well as those that encode mitochondrial proteins.

  • We speculate that operons facilitate global regulation of the basic gene expression and energy generation machinery of the cell, in response to signals that are unknown at present.

Abstract

Nematodes are unusual among animals in having a substantial proportion of their genes arranged in polycistronic clusters that are similar to bacterial operons. Recently, a nearly complete database of the Caenorhabditis elegans genes that are transcribed in operons has been produced. Analysis of this database has identified the types of genes that are contained in the operons and the extent to which operons co-regulate genes of related function.

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Figure 1: The first operon identified in Caenorhabditis elegans.
Figure 2: Percentage of genes of various classes encoded in operons.

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Acknowledgements

We are grateful to P. MacMorris for comments on the manuscript, to J. Ahringer for the communication of results before publication, and to A. Skop, K. Howell, S. Adam, A. Page, A. van Hoof and W. Harper for providing gene lists. The authors are supported by the National Institute of General Medical Sciences.

Author information

Authors and Affiliations

  1. Department of Biochemistry and Molecular Genetics, Box B-121, University of Colorado School of Medicine, Denver, 80262, Colorado, USA

    Thomas Blumenthal & Kathy Seggerson Gleason

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  1. Thomas Blumenthal
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  2. Kathy Seggerson Gleason
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Correspondence to Thomas Blumenthal.

Related links

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Databases

FlyBase

Adh

Adhr

stoned

Locuslink

GDF1

LASS1

WormBase

C14B1.7

C14B1.8

F43C1.3

gpd-1

gpd-2

gpd-3

gst-1

mai-1

R107.6

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Y47G6A.24

Y47G6A.25

Further information

Steve Mount's lab

Glossary

ARCHAEA

An ancient group of organisms that have ribosomes and cell membranes that distinguish them from bacteria. They are often found in extreme environments, such as near deep-sea vents.

POLYCISTRONIC

Clusters that contain several adjacent cistrons (or genes).

TRANS-SPLICING

A process closely related to intron removal, in which a short spliced leader is spliced onto the 5′ ends of mRNAs.

RNA INTERFERENCE

(RNAi). A process by which double-stranded RNA silences specifically the expression of homologous genes through degradation of their cognate mRNA.

SECONDARY TRANSPORTER

A membrane transporter that does not require ATP cleavage for transport.

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Blumenthal, T., Gleason, K. Caenorhabditis elegans operons: form and function. Nat Rev Genet 4, 110–118 (2003). https://doi.org/10.1038/nrg995

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