HDAC6 regulates DNA damage response via deacetylating MLH1

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• MutL homolog 1 (MLH1) is crucial for genomic stability and DNA damage response.
• MLH1 is a key component of the DNA mismatch repair (MMR) system.

Purpose of the Study:

• To investigate the regulatory role of histone deacetylase 6 (HDAC6) on MLH1.
• To elucidate the impact of MLH1 acetylation status on DNA damage response and repair complex formation.

Main Methods:

• In vitro and in vivo biochemical assays to study protein interactions and enzymatic activity.
• Mass spectrometry (MS) analysis to identify novel acetylation sites on MLH1.
• Site-directed mutagenesis to create acetylation and deacetylation mimetic mutants of MLH1.

Main Results:

• HDAC6 directly interacts with and deacetylates MLH1.
• Deacetylation of MLH1 by HDAC6 inhibits the assembly of the MutSα-MutLα complex.
• Four novel acetylation sites on MLH1 were identified.
• A deacetylation-mimetic MLH1 mutant conferred resistance to 6-thioguanine, unlike wild-type or acetylation-mimetic mutants.

Conclusions:

• HDAC6 negatively regulates MLH1 function through deacetylation.
• HDAC6-mediated deacetylation of MLH1 disrupts the DNA damage sensor complex (MutSα-MutLα).
• This disruption leads to impaired DNA damage response and increased tolerance to genotoxic stress.