Tom Blumenthal et al. (2001) International C. elegans Meeting "A Global Analysis of the Caenorhabditis elegans Operons"

Alessandro Guffanti, Chris Link, Stuart Kim, Donald Evans, Kyle Duke, Daniel Lawson, Jean Thierry-Mieg, Tom Blumenthal, Danielle Thierry-Mieg

[International C. elegans Meeting, 2001]

Unlike genomes of other animals, the genomes of Caenorhabditis elegans and its close relatives contain numerous polycistronic transcription units similar to bacterial operons. The pre-mRNAs from these operons are processed into monocistronic mRNAs by 3' end formation and a specialized form of trans-splicing using the spliced leader, SL2. In order to determine how widespread operons are in the C. elegans genome, we have probed microarrays containing 17,817 predicted and known genes with a probe specific for mRNAs containing the SL2 sequence along with a control probe to polyA+ RNA. There are 1215 genes that form a separate group with high SL2/polyA+ ratios at the 99.9% level of confidence, and 86% of these appear to be downstream genes in operons, based on their genomic arrangements. We integrated this list with a list of ~400 genes in known operons and/or with confirmed SL2-containing cDNA clones. Of the genes previously confirmed to be SL2 trans-spliced, 91% are contained on the list of operons based on the microarray experiment, and almost all are in downstream positions. We estimate the genome contains ~850 operons, of which we provide experimental support for 807. On average, the operons contain 2.6 genes, and the longest contain seven genes. At least 13% of C. elegans genes are transcribed polycistronically. Operons are relatively common on chromosomes I and III, but much rarer on V and especially X. The average spacing between the polyA site of the upstream gene and the trans-splice site of the downstream gene is 126 bp. Most of the operons uncovered in this analysis have not been reported previously, and we can cite numerous new examples of co-transcription of genes encoding apparently functionally related proteins. We suggest the possibility that close inspection of the operon list could reveal heretofore unknown protein relationships.

Prasad Kasturi et al. (2006) European Worm Meeting "MOG-3 Links Sex Determination to GLP-1/Notch Signaling"

Alessandro Puoti, Prasad Kasturi

[European Worm Meeting, 2006]

Prasad Kasturi and Alessandro Puoti. The hermaphroditic nematode Caenorhabditis elegans sequentially produces both sperm and oocytes from a single pool of germ cell precursors. After the brief period of spermatogenesis during the fourth larval stage, the adult produces oocytes for the rest of its life. The events that regulate the fate of germ cells are at least in part controlled post-transcriptionally: While the entry into meiosis and its progression require the silencing of the glp-1 mRNA, the switch from spermatogenesis to oogenesis is dependent on post-transcriptional repression of the fem-3 mRNA.. To understand the molecular mechanisms that govern fem-3 repression, several trans-acting factors have been identified in genetic and biochemical screens. The mog genes have been shown to repress fem-3 mRNA through its 3 untranslated region. Four cloned mog genes code for nuclear proteins that are homologous to RNA processing factors. In addition these MOG proteins directly bind to the nuclear zinc finger protein MEP-1 that is also required for fem-3 repression. We have cloned the mog-3 by SNP mapping and candidate gene approach. mog-3 encodes a conserved nuclear protein that shares weak homology to a spliceosomal complex protein in fission yeast. A mog-3::gfp transgene is expressed in the nuclei of many somatic cells. MOG-3 binds to MEP-1 in a similar fashion as the other MOG proteins. Similar to other mog genes mog-3 also play a role in the mitosis to meiosis switch.. To investigate the molecular function of MOG-3, a yeast two-hybrid system was used to screen the interacting factors. One of the interacting protein (CIR) is a co-repressor of LAG-1. CIR also interacts with MEP-1. Since MEP-1 is a part of the NuRD complex, we speculate that CIR and MOG-3 with MEP-1 may form a complex to regulate target genes in the GLP-1/Notch pathway.. Keywords & Abbreviations: Germline, Sex determination, Post-transcriptional regulation, mog (masculanization of germ line), fem (feminization), mep (mog interacting and ectopic P granules), gld (germ line defective), SNP (Single Nucleotide Polymorphism) and NuRD (nucleosome remodeling and deacetylation), glp (germline proliferative) and Notch signaling.