module: dmel_mediator_complex
title: Mediator complex in Drosophila melanogaster
label: Mediator complex
module_type: PROTEIN_COMPLEX
description: >-
  Mediator is a large multisubunit coactivator that bridges DNA-bound
  transcription factors and RNA polymerase II, helping assemble and activate the
  preinitiation complex. The core Mediator (head, middle and tail modules,
  with MED14 as a central scaffold) binds the polymerase, while tail subunits
  contact activators. The CDK8 kinase module (CKM), consisting of Cdk8, CycC,
  MED12 (kto) and MED13 (skd), associates reversibly with core Mediator and
  generally restrains its interaction with polymerase; Drosophila kto and skd
  were identified through their roles in imaginal disc patterning.
summary: >-
  Core Mediator coactivator and its reversibly associated CDK8 kinase module.
concepts:
  - {id: GO:0016592, label: mediator complex}
cellular_components:
  - {id: GO:0005634, label: nucleus}
parts:
  - id: core_mediator
    label: Core Mediator
    role: activator-polymerase bridge
    group: MED
    complex_term: {id: GO:0016592, label: mediator complex}
  - id: ckm
    label: CDK8 kinase module
    role: regulatory kinase module
    group: CKM
    complex_term: {id: GO:1990508, label: CKM complex}
    unit_functions:
      Cdk8: {id: GO:0008353, label: RNA polymerase II CTD heptapeptide repeat kinase activity}
connections:
  - {source: ckm, target: core_mediator, connection_type: NEGATIVELY_REGULATES, description: CKM binding to core Mediator restrains its association with RNA polymerase II.}
notes: >-
  Boundary. The core is modelled as a single complex because head, middle and
  tail assignments of several metazoan-specific subunits (MED26-MED30) are not
  uniform across studies. ix is the Drosophila MED29.