Metastatic tumor antigen 1 contributes to hepatocarcinogenesis posttranscriptionally through RNA-binding function

Area of Science:

• Molecular Biology
• Oncology
• Hepatology

Background:

• Metastatic tumor antigen 1 (MTA1) is implicated in hepatocellular carcinoma (HCC) tumorigenesis.
• While nuclear MTA1's role as a chromatin modifier is known, cytoplasmic MTA1's function in carcinogenesis remains unclear.
• This study investigates the posttranscriptional regulatory role of cytoplasmic MTA1.

Purpose of the Study:

• To elucidate the molecular mechanisms of cytoplasmic MTA1 in HCC.
• To determine if MTA1 directly interacts with MYC RNA.
• To assess the clinical relevance of cytoplasmic MTA1 and its interaction with MYC in HBV-HCC patients.

Main Methods:

• In vitro and in vivo RNA-protein interaction assays.
• Gain- and loss-of-function experiments using wild-type MTA1 and a G78D mutant.
• RNA-immunoprecipitation sequencing (RIP-seq).
• Analysis of HBV-HCC patient cohorts.

Main Results:

• MTA1 directly binds to the 3'-untranslated region of MYC RNA.
• A specific mutation (G78D) abolished MTA1's RNA-binding activity and its ability to stabilize MYC.
• MTA1, but not the mutant, extended MYC half-life and reduced its degradation, promoting tumorigenesis.
• RIP-seq identified other oncogenesis-related mRNAs bound by MTA1.
• High cytoplasmic MTA1 levels and MTA1-MYC interaction correlated with early recurrence in HBV-HCC.

Conclusions:

• MTA1 functions as a generic RNA-binding protein.
• Cytoplasmic MTA1 regulates gene expression posttranscriptionally by binding to MYC RNA.
• This interaction contributes to hepatocarcinogenesis and is associated with early recurrence in HBV-HCC.