TIP60 represses activation of endogenous retroviral elements

Area of Science:

• Molecular Biology
• Epigenetics
• Cancer Research

Background:

• TIP60, a lysine acetyltransferase, functions as a haplo-insufficient tumor suppressor.
• TIP60 downregulation is an early event in tumorigenesis, observed in breast and colorectal cancers.
• The precise mechanisms of TIP60's tumor-regulatory functions remain incompletely understood.

Purpose of the Study:

• To elucidate the role of TIP60 in regulating endogenous retroviral elements (ERVs).
• To investigate the molecular mechanisms underlying TIP60's tumor suppressive functions.
• To identify novel therapeutic targets in colorectal cancer.

Main Methods:

• Investigated TIP60's role in ERV silencing using molecular biology techniques.
• Assessed the dependency of TIP60-mediated ERV silencing on BRD4.
• Analyzed the regulation of histone methyltransferases SUV39H1 and SETDB1 by TIP60 and BRD4.
• Examined the impact of TIP60 loss on genome-wide retrotransposon activity and inflammatory pathways in colorectal cancer models.

Main Results:

• TIP60 mediates the silencing of endogenous retroviral elements (ERVs) in a BRD4-dependent manner.
• TIP60 and BRD4 co-regulate SUV39H1 and SETDB1, impacting global H3K9 trimethylation levels.
• Loss of TIP60 in colorectal cancer leads to de-repression of retrotransposons, activating the STING-mediated cellular response to pathogens.
• This activation results in the induction of Interferon Regulatory Factor 7 (IRF7) and associated inflammatory responses.

Conclusions:

• TIP60 and BRD4 regulate ERV silencing through histone H3 K9 trimethylation.
• TIP60 plays a critical role in suppressing tumor progression by maintaining ERV silencing and preventing aberrant inflammatory responses.
• This study uncovers a novel tumor suppressive mechanism of TIP60 in vivo, offering potential therapeutic avenues for colorectal cancer.