Cryo-EM structure of the Smc5/6 holo-complex

Area of Science:

• Structural Biology
• Molecular and Cell Biology
• Biochemistry

Background:

• The Smc5/6 complex is crucial for DNA repair, replication stress response, and antiviral defense.
• Understanding its structure is key to elucidating its diverse cellular functions.

Purpose of the Study:

• To determine the high-resolution structure of the budding yeast Smc5/6 holo-complex.
• To understand the interaction between the Smc5/6 core and the Nse1/3/4 subcomplex.
• To investigate the functional consequences of disrupting Smc5/6 interactions.

Main Methods:

• Reconstitution of the Smc5/6 holo-complex from recombinant proteins.
• Cryogenic electron microscopy (cryo-EM) for structural determination.
• Site-directed mutagenesis and live-cell single molecule localization microscopy (SMLM).

Main Results:

• The cryo-EM structure provides an architectural overview of the six-subunit Smc5/6 complex.
• A specific loop in Smc5 (Smc5-loop) interacts with the Nse1 subunit.
• Mutations in Nse1 affecting Smc5-loop binding cause slow growth and reduced chromatin association of Smc5/6.
• Functional equivalence between KITE and HAWK accessory subunits was suggested.

Conclusions:

• The Smc5/6 structure reveals critical interactions for complex assembly and function.
• The Smc5-loop/Nse1 interaction is essential for Smc5/6 chromatin localization and cell viability.
• Structural insights support functional parallels between different SMC complex accessory subunits.