Subnuclear Relocalization of Structure-Specific Endonucleases in Response to DNA Damage.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Structure-specific endonucleases are crucial for maintaining genome integrity by resolving DNA structures during repair, replication, and recombination.
• The response of these endonucleases, particularly Mus81-Mms4/EME1, to genotoxic stress remains incompletely understood.

Purpose of the Study:

• To investigate the dynamic behavior and localization of the Mus81-Mms4/EME1 endonuclease in response to DNA damage.
• To elucidate the regulatory mechanisms, including protein interactions and ubiquitination, governing Mus81-Mms4/EME1 recruitment and function at DNA damage sites.

Main Methods:

• Immunofluorescence microscopy to observe the subnuclear localization of Mus81-Mms4/EME1 and other relevant proteins.
• Genetic analysis to determine the roles of ubiquitin-conjugating enzyme Rad6 and E3-ubiquitin ligase Bre1 in foci formation.
• Analysis of foci dynamics in relation to DNA intermediates requiring Mus81-Mms4/EME1 resolution and Mms4 phosphorylation.

Main Results:

• Mus81-Mms4/EME1 relocalizes to distinct subnuclear foci upon DNA damage, co-localizing with Rad1-Rad10 (XPF-ERCC1) and Slx1-Slx4.
• Recruitment to these stress foci, defined by Cmr1/WDR76, is dependent on Rad6 and Bre1.
• Mus81 foci exhibit dynamic behavior, persisting until Mms4 phosphorylation activates the endonuclease, particularly when DNA intermediates requiring its action are present.

Conclusions:

• Subnuclear relocalization of Mus81-Mms4/EME1 to stress foci is a key response to genotoxic stress.
• The recruitment and function of Mus81-Mms4/EME1 are regulated by ubiquitination pathways involving Rad6 and Bre1.
• These findings highlight the functional relevance of dynamic relocalization and regulation for structure-specific endonucleases in maintaining genome stability.