A component of the transcriptional mediator complex inhibits RAS-dependent vulval fate specification inC. elegans

Abstract

Negative regulation of receptor tyrosine kinase (RTK)/RAS signaling pathways is important for normal development and the prevention of disease in humans. We have used a genetic screen in C. elegans to identify genes that antagonize the activity of activated LET-23, a member of the EGFR family of RTKs. We identified two loss-offunction mutations in dpy-22, previously cloned as sop-1, that promote the ability of activated LET-23 to induce ectopic vulval fates. DPY-22 is a glutamine-rich protein that is most similar to human TRAP230, a component of a transcriptional mediator complex. DPY-22 has previously been shown to regulate WNT responses through inhibition of the β-catenin-like protein BAR-1. We provide evidence that DPY-22 also inhibits RAS-dependent vulval fate specification independently of BAR-1, and probably regulates the activities of multiple transcription factors during development. Furthermore, we demonstrate that although inhibition of BAR-1-dependent gene expression has been shown to require the C-terminal glutamine-rich region, this region is dispensable for inhibition of RASdependent cell differentiation. Thus, the glutamine-rich region contributes to specificity of this class of mediator protein.

The Mediator Kinase Module Restrains Epidermal Growth Factor Receptor Signaling and Represses Vulval Cell Fate Specification in Caenorhabditis elegans

“…We next investigated whether cdk-8, like mdt-12/dpy-22 (Moghal and Sternberg 2003a), also represses vulval induction. Indeed, cdk-8 and cic-1(tm3740) null mutants displayed a low penetrance Muv phenotype, as measured both by VPC induction analysis in L4 animals (Table 1) and by scoring the occurrence of ectopic vulval protrusions in adult worms (Figure 2B; see statistical comparisons between L4 and adult Muv scores, Table S2).…”

“…Furthermore, in Saccharomyces cerevisiae, the CKM regulates the activity of the Mediator tail module subunits MED2, MED3, and MED15 (van de Peppel et al 2005;Gonzalez et al 2014). However, whether such intra-Mediator signaling effects occur in metazoans and affect e.g., animal development has not yet been tested.Several Mediator subunits including at least one CKM subunit regulate vulva development in Caenorhabditis elegans Singh and Han 1995;Kwon and Lee 2001;Moghal and Sternberg 2003a). The study of cell fate specification in the C. elegans vulva has proven a powerful way to identify the components and regulatory interactions of several evolutionarily conserved signaling pathways (Félix and Barkoulas 2012;Schmid and Hajnal 2015).…”

“…Several Mediator subunits including at least one CKM subunit regulate vulva development in Caenorhabditis elegans Singh and Han 1995;Kwon and Lee 2001;Moghal and Sternberg 2003a). The study of cell fate specification in the C. elegans vulva has proven a powerful way to identify the components and regulatory interactions of several evolutionarily conserved signaling pathways (Félix and Barkoulas 2012;Schmid and Hajnal 2015).…”

The zebrafish kohtalo/trap230 gene is required for the development of the brain, neural crest, and pronephric kidney

“…Mutant cells proliferate, survive, and initiate but do not complete differentiation; most notably, these cells do not respect compartment boundaries, leading to disorganized tissue architecture (10,11). In Caenorhabditis elegans, the TRAP230 homolog is an essential gene (12,13) and is required for asymmetric cell division in the T blast cell lineage (14). Vertebrate mutations in the gene encoding TRAP230 have not been reported.…”

gon-14 Functions With Class B and Class C Synthetic Multivulva Genes to Control Larval Growth in Caenorhabditis elegans

“…Scoring phenotypes: VPC induction: Induction of the VPCs, P3.p-P8.p, was scored in mid-to-late L4 stage larvae, essentially as described (Moghal and Sternberg 2003). Each VPC was assigned a score of 1 if both daughters had divided, 0.5 if only one daughter had divided, or 0 if neither one had divided.…”