ARC coactivator complex

Stable Identifier
R-HSA-212374
Type
Complex
Species
Homo sapiens
Compartment
Locations in the PathwayBrowser
Summation

MED1 is a component of each of the various Mediator complexes, that function as transcription co-activators. The MED1-containing compolexes include the DRIP, ARC, TRIP and CRSP compllexes.

Summary: ARC co-activator complex and assembly The ARC coactivator complex is a subset of 19 proteins from the set of at least 31 Mediator proteins that, in different combinations, form "Adapter" complexes (Figure 1). Adapter complexes bridge between the basal transcription factors (including Pol II) and tisue-specific transcrption factors (TFs) bound to sites within upstream Proximal Promoter regions or distal Enhancer regions (reviewed in Maston, 2006 and Naar, 2001). The ARC complex contains the 15 components present in the DRIP complex, as well as 4 additional components (Rachez, 1999), These ARC-specific components are now called: MED8, MED15, MED25, and MED 26 in the unified nomenclature scheme (Bourbon, 2004). The 15 ARC complex components that are shared with the DRIP complex components, are also shared with the TRAP coactivator complex. However, the TRAP complex also has 4 additional, distinct components (Bourbon, 2004), which are now called: MED20, MED27, MED30, and MED 31 in the unified nomenclature scheme. The ARC complex was originally identified and named as a co-activator complex associated with transcription activator proteins (reviewed in Malik, 2005 and references therein). It was subsequently determined that all of the components of the DRIP complex are also in the ARC complex, and in the TRAP complex. In addition, these various transcription co-activator proteins identified in mammalian cells were found to be the orthologues or homologues of the Mediator complex proteins in yeast, first identified by Kornberg and colleagues (Kelleher, 1990). The unified nomenclature system for these adapter / co-activator proteins now labels them Mediator 1 through Mediator 31 (Bourbon, 2004). The order of addition of the ARC proteins during complex assembly is not fully determined, and may vary in different cell contexts. Therefore, ARC complex assembly is represented as a single reaction, in which all 19 components assemble simultaneously into the ARC co-activator complex.

DRIP co-activator complex and assembly

The DRIP co-activator complex is a subset of 14 proteins from the set of at least 31 Mediator proteins that, in different combinations, form "Adapter" complexes. Adapter complexes bridge between the basal transcription factors (including Pol II) and tissue-specific transcription factors (TFs) bound to sites within upstream Proximal Promoter regions or distal Enhancer regions (reviewed in Maston, 2006 and Naar, 2001).

The DRIP complex was originally identified and named as a co-activator complex associated with the Vitamin D Receptor member of the nuclear receptor family of transcription factors (Rachez, 1998). It was later determined that all of the components of the DRIP complex were also in the TRAP complex, and the ARC complex.

The DRIP complex contains the following 14 proteins, which also are common to the ARC and TRAP complexes: MED1, MED4, MED6, MED7, MED10, MED12, MED13, MED14, MED16, MED17, MED23, MED24, CDK8, CycC.

All of the DRIP adapter complex components are present in the ARC adapter complex, but the ARC complex also has 4 additional components (Rachez, 1999). These ARC-specific components are now called: MED8, MED15, MED25, and MED 26 in the unified nomenclature scheme (Bourbon, 2004).

Similarly, all 14 of the DRIP adapter complex components are present in the TRAP adapter complex, but the TRAP complex also has 4 additional components (Bourbon, 2004), These TRAP-specific components are now called: MED20, MED27, MED30, and MED 31 in the unified nomenclature scheme.

In addition, these various transcription co-activator proteins identified in mammalian cells were found to be the orthologues or homologues of the Mediator complex identified in yeast, first identified by Kornberg and colleagues (Kelleher, 1990).

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