Recombinant Mouse Mediator of RNA polymerase II transcription subunit 16 (Med16), partial

Introduction to Recombinant Mouse Mediator of RNA Polymerase II Transcription Subunit 16 (Med16), Partial

The Mediator complex is a multi-subunit assembly essential for regulating the expression of most RNA polymerase II (Pol II) transcripts . These transcripts include protein-coding and most non-coding RNA genes . Within this complex, the Med16 subunit plays a crucial role in gene regulation . Med16 acts as a conduit, transmitting signals to RNA polymerase II (RNAP II) and is essential for cytoprotection against oxidative insults .

Structure and Function of Med16

Med16 is a component of the Mediator complex, which interacts with gene-specific transcription factors and the RNA polymerase II transcription machinery . The Mediator complex helps to stabilize and initiate transcription .

Key structural and functional aspects of Med16 include:

• Interaction with NRF2: Med16 directly associates with NRF2 (Nuclear factor erythroid 2-related factor 2), a transcription factor that activates antioxidant genes .

• Functional Domains: Mouse Med16 has two predicted functional domains: a WD repeat-like domain and a MED16 conserved region .

• Role in Transcription: Med16 is required for NRF2-dependent phosphorylation of the RNA Polymerase II C-terminal domain . Disruption of Med16 significantly attenuates the expression of NRF2 target genes .

Med16's Role in Gene Expression

Med16 influences gene expression by acting as a coactivator. It is required for the recruitment of RNA Pol II and its progression along genes .

• Cold-Regulated Genes: In Arabidopsis, MED16 influences cold-regulated gene expression and is required for the recruitment of RNA Pol II to cold-inducible genes .

• NRF2-Mediated Gene Expression: Med16 serves as a key component of the Mediator complex for NRF2-mediated gene expression. It is required for the inducible expression of a majority of NRF2 target genes .

Med16 and the KEAP1-NRF2 Pathway

The KEAP1-NRF2 system plays a central role in cytoprotection .

• Antioxidant Response: The KEAP1-NRF2-MED16 axis is a regulatory pathway mediating the antioxidant response through the activation of NRF2 target genes .

• Electrophile-Induced Expression: Med16 is specifically required for NRF2-dependent transcription and the electrophile-induced expression of NRF2 target genes .

Experimental Evidence of Med16 Function

Research has provided evidence supporting the role of Med16 in transcriptional regulation:

• Direct Interaction with NRF2: Recombinant MED16 interacts efficiently with GST-Neh4/5, a component of the NRF2 protein complex, confirming a direct interaction between NRF2 and MED16 .

• Med16 Knockout Studies: Studies using Med16 knockout cell lines show that MED16 is required for NRF2-dependent phosphorylation of the RNAP II C-terminal domain .

• ChIP Analysis: Chromatin immunoprecipitation (ChIP) assays demonstrate that MED16 does not influence the availability of NRF2 at AREs (antioxidant response elements) but is required for RNAP II recruitment to NRF2 target gene loci .

Implications for RNA Polymerase II Transcription

The Mediator complex, including Med16, is integral to RNA polymerase II transcription.

• Regulation of Transcription: Mediator regulates many steps of RNAPII transcription and connects transcription with co-transcriptional events .

• Interaction with Transcription Factors: Mediator interacts with gene-specific transcription factors at enhancers and with the RNAPII transcription machinery .

• Conformational Changes: The Mediator complex reorganizes its conformation and composition while making transient contacts with other components involved in transcription, chromatin regulation, and mRNA processing .

Tables Summarizing Key Findings

Table 1: Med16 Interaction with NRF2

Table 2: Med16 Role in NRF2-Dependent Transcription