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Published on: November 11, 2016
A Peptidomimetic Ligand Targeting the Chromodomain of MPP8 Reveals HRP2's Association with the HUSH Complex
Jarod M Waybright1, Sarah E Clinkscales1, Kimberly D Barnash
1Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States.
Abstract:
The interpretation of histone post-translational modifications (PTMs), specifically lysine methylation, by specific classes of "reader" proteins marks an important aspect of epigenetic control of gene expression. Methyl-lysine (Kme) readers often regulate gene expression patterns through the recognition of a specific Kme PTM while participating in or recruiting large protein complexes that contain enzymatic or chromatin remodeling activity. Understanding the composition of these Kme-reader-containing protein complexes can serve to further our understanding of the biological roles of Kme readers, while small molecule chemical tools can be valuable reagents in interrogating novel protein-protein interactions. Here, we describe our efforts to target the chromodomain of M-phase phosphoprotein 8 (MPP8), a member of the human silencing hub (HUSH) complex and a histone 3 lysine 9 trimethyl (H3K9me3) reader that is vital for heterochromatin formation and has specific roles in cancer metastasis. Utilizing a one-bead, one-compound (OBOC) combinatorial screening approach, we identified UNC5246, a peptidomimetic ligand capable of interacting with the MPP8 chromodomain in the context of the HUSH complex. Additionally, a biotinylated derivative of UNC5246 facilitated chemoproteomics studies which revealed hepatoma-derived growth factor-related protein 2 (HRP2) as a novel protein associated with MPP8. HRP2 was further shown to colocalize with MPP8 at the E-cadherin gene locus, suggesting a possible role in cancer cell plasticity.
Insights
Researchers identified a novel compound targeting the MPP8 protein, a key player in gene regulation and cancer metastasis. This discovery aids in understanding protein interactions within the HUSH complex and its role in epigenetic control.
Area of Science:
- Epigenetics
- Molecular Biology
- Cancer Research
Background:
- Histone post-translational modifications (PTMs), particularly lysine methylation (Kme), are crucial for epigenetic gene regulation.
- Kme reader proteins interpret these modifications, often by forming large complexes with enzymatic or chromatin remodeling activities.
- Understanding these complexes is vital for elucidating Kme reader functions and developing chemical tools.
Purpose of the Study:
- To target the chromodomain of M-phase phosphoprotein 8 (MPP8), a histone 3 lysine 9 trimethyl (H3K9me3) reader within the human silencing hub (HUSH) complex.
- To identify novel protein-protein interactions associated with MPP8 using chemical biology approaches.
- To investigate the role of MPP8 and its interacting partners in cancer metastasis and cell plasticity.
Main Methods:
- Employed a one-bead, one-compound (OBOC) combinatorial screening approach to identify MPP8 chromodomain ligands.
- Synthesized a peptidomimetic ligand, UNC5246, and its biotinylated derivative.
- Utilized chemoproteomics with the biotinylated UNC5246 to identify interacting proteins and performed colocalization studies.
Main Results:
- Identified UNC5246, a peptidomimetic ligand that interacts with the MPP8 chromodomain within the HUSH complex.
- Discovered hepatoma-derived growth factor-related protein 2 (HRP2) as a novel protein associated with MPP8 through chemoproteomics.
- Demonstrated colocalization of HRP2 and MPP8 at the E-cadherin gene locus, suggesting a role in cancer cell plasticity.
Conclusions:
- UNC5246 serves as a valuable chemical tool for studying MPP8 and the HUSH complex.
- The identification of HRP2 as an MPP8-interacting protein provides new insights into heterochromatin regulation and cancer biology.
- MPP8 and HRP2's colocalization at the E-cadherin locus suggests a potential mechanism for MPP8's role in cancer cell plasticity and metastasis.
