Chromatin regulation and sumoylation in the inhibition of Ras-induced vulval development in Caenorhabditis elegans - PubMed (original) (raw)

Chromatin regulation and sumoylation in the inhibition of Ras-induced vulval development in Caenorhabditis elegans

Gino Poulin et al. EMBO J. 2005.

Erratum in

Abstract

In Caenorhabditis elegans, numerous 'synMuv' (synthetic multivulval) genes encode for chromatin-associated proteins involved in transcriptional repression, including an orthologue of Rb and components of the NuRD histone deacetylase complex. These genes antagonize Ras signalling to prevent erroneous adoption of vulval fate. To identify new components of this mechanism, we performed a genome-wide RNA interference (RNAi) screen. After RNAi of 16 757 genes, we found nine new synMuv genes. Based on predicted functions and genetic epistasis experiments, we propose that at least four post-translational modifications converge to inhibit Ras-stimulated vulval development: sumoylation, histone tail deacetylation, methylation, and acetylation. In addition, we demonstrate a novel role for sumoylation in inhibiting LIN-12/Notch signalling in the vulva. We further show that many of the synMuv genes are involved in gene regulation outside the vulva, negatively regulating the expression of the Delta homologue lag-2. As most of the genes identified in this screen are conserved in humans, we suggest that similar interactions may be relevant in mammals for control of Ras and Notch signalling, crosstalk between these pathways, and cell proliferation.

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Figures

Figure 1

Figure 1

Vulval cell fate specification by the inductive and lateral signals. (A) The inductive signal emanates from the AC. The AC secretes LIN-3 EGF inducing vulval fates in P(5–7).p, which will produce 22 vulval cells. The remaining VPCs have the 3° cell fate, dividing once (dashed circles) and fusing to the hypoderm hyp7. (B) Upon activation of the Ras signalling pathway in P6.p, LIN-12/NOTCH is downregulated in a Ras-dependant manner and its ligands (LAG-2, APX-1, and DSL-1) are expressed, mediating the lateral signal essential for expression of the 2° fate in P5.p and P7.p. In these cells, Notch signalling is activated and negative regulators of Ras are upregulated, reducing Ras signalling.

Figure 2

Figure 2

The Muv phenotype. (A) Wild-type N2 adult with normal vulva (arrow). (B) lin-15B(n744); lin-15A(RNAi) adult with multiple vulval protrusions. Arrowheads point to extra vulvae and the arrow to the normal vulva.

Figure 3

Figure 3

HDA-1 is sumoylated. Western blot of wild-type (lane 1) or smo-1 SUMO mutant (lane 2) total worm extract, probed with an anti-HDA-1 antibody. The N2 (WT) extract shows a fast-migrating band at about 65 kDa and a slow-migrating band at about 75 kDa. The slow-migrating band is absent from smo-1 SUMO mutant extract.

Figure 4

Figure 4

The lag-2_∷_gfp reporter assay. (A) Wild-type mid-L4 stage worm carrying the lag-2_∷_gfp reporter shows strong expression only in the distal tip cells (white arrows) and the vulva (white arrowheads). RNAi of T22D1.10 ruvb-2 helicase (B) or K12C11.2 smo-1 (C) induces strong ectopic expression of lag-2_∷_gfp in the intestine. Only one DTC is visible in the focal plane shown in (C). (D) RNAi of T14G8.1 chd-3 does not induce ectopic lag-2_∷_gfp expression.

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