Component of the Mediator complex, a coactivator involved in regulated gene transcription of nearly all RNA polymerase II-dependent genes. Mediator functions as a bridge to convey information from gene-specific regulatory proteins to the basal RNA polymerase II transcription machinery. Mediator is recruited to promoters by direct interactions with regulatory proteins and serves as a scaffold for the assembly of a functional pre-initiation complex with RNA polymerase II and the general transcription factors (By similarity). Functions downstream of receptor let-23 and let-60/Ras during vulval induction likely by down-regulating the expression of phosphatase dep-1 and lin-12/Notch in vulva precursor cell descendants with a primary cell fate (PubMed:7557379, PubMed:15901674). Acts to repress beta-catenin target genes (PubMed:12130541). Required for asymmetric division of T-cells (PubMed:15790964). Plays a role in responses to M.nematophilum-mediated bacterial infection by promoting tail swelling and preventing constipation (PubMed:15268855). Component of the Mediator complex (By similarity). Interacts with let-19/mdt-13. Highest levels in embryos and larvae. Expressed in vulval precursor cells at the time of vulval determination. Belongs to the Mediator complex subunit 23 family.