Structural insights into the assembly and function of the SAGA deubiquitinating module

Area of Science:

• Molecular Biology
• Structural Biology
• Epigenetics

Background:

• The SAGA complex is a crucial eukaryotic transcriptional coactivator involved in gene activation and elongation.
• A key function of SAGA is the deubiquitination of histone H2B, mediated by its deubiquitinating module (DUBm).

Purpose of the Study:

• To elucidate the structural basis of the DUBm's deubiquitinating activity.
• To understand the roles of individual DUBm components and zinc atoms in complex formation and function.

Main Methods:

• X-ray crystallography was employed to determine the structures of the DUBm, both alone and bound to ubiquitin aldehyde.
• High-resolution structures (1.90 Å and 2.45 Å) were obtained for detailed atomic analysis.

Main Results:

• The crystal structure reveals a highly interconnected DUBm complex stabilized by eight essential structural zinc atoms.
• The arrangement of protein domains suggests a mechanism for Ubp8 activation by other DUBm proteins.
• The structure provides a framework for understanding DUBm interaction with monoubiquitinated histone H2B.

Conclusions:

• The DUBm's structure highlights the critical role of protein-protein interactions and zinc coordination in histone deubiquitination.
• These findings offer molecular insights into epigenetic regulation mediated by histone modification and SAGA complex function.