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Updated: Dec 11, 2025
Live-3D-Cell Immunocytochemistry Assays of Pediatric Diffuse Midline Glioma
Published on: November 11, 2021
RACK7 recognizes H3.3G34R mutation to suppress expression of MHC class II complex components and their delivery
Fangfang Jiao1, Ze Li2,3, Chen He4
1Center for Medical Research and Innovation, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, and the Shanghai Key Laboratory of Medical Epigenetics, the International Co-laboratory of Medical Epigenetics and Metabolism, Ministry of Science and Technology, Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China.
Abstract:
Histone H3 point mutations have been identified in incurable pediatric brain cancers, but the mechanisms through which these mutations drive tumorigenesis are incompletely understood. Here, we provide evidence that RACK7 (ZMYND8) recognizes the histone H3.3 patient mutation (H3.3G34R) in vitro and in vivo. We show that RACK7 binding to H3.3G34R suppresses transcription of CIITA, which is the master regulator of MHC (major histocompatibility complex) class II molecules and genes involved in vesicular transport of MHC class II molecules to the cell surface, resulting in suppression of MHC class II molecule expression and transport. CRISPR-based knock-in correction of the H3.3G34R mutation in human pediatric glioblastoma (pGBM) cells significantly reduces overall RACK7 chromatin binding and derepresses the same set of genes as does knocking out RACK7 in the H3.3G34R pGBM cells. By demonstrating that H3.3G34R and RACK7 work together, our findings suggest a potential molecular mechanism by which H3.3G34R promotes cancer.
Insights
Histone H3 mutations in pediatric brain cancers are linked to RACK7 binding, which suppresses CIITA and MHC class II expression. Correcting the mutation reduces RACK7 binding and restores gene expression, revealing a cancer mechanism.
Area of Science:
- Oncology
- Molecular Biology
- Epigenetics
Background:
- Histone H3 point mutations are implicated in pediatric brain cancers.
- The precise mechanisms driving tumorigenesis by these mutations remain unclear.
Purpose of the Study:
- To investigate the role of RACK7 (ZMYND8) in recognizing and responding to the H3.3G34R mutation in pediatric brain tumors.
- To elucidate the downstream effects of this interaction on gene expression and cellular processes.
Main Methods:
- In vitro and in vivo binding assays to assess RACK7 interaction with H3.3G34R.
- CRISPR-based gene editing to correct the H3.3G34R mutation in pediatric glioblastoma (pGBM) cells.
- Analysis of CIITA and MHC class II molecule expression and transport.
Main Results:
- RACK7 directly recognizes the H3.3G34R mutation.
- RACK7 binding to H3.3G34R suppresses transcription of CIITA, the master regulator of MHC class II.
- This leads to reduced MHC class II expression and impaired transport, a phenotype reversed by correcting the H3.3G34R mutation or knocking out RACK7.
Conclusions:
- H3.3G34R and RACK7 cooperate to promote pediatric brain tumorigenesis.
- The findings suggest a novel molecular mechanism involving epigenetic alterations and immune evasion in pediatric gliomas.
