Structural insight into the assembly and conformational activation of human origin recognition complex

Area of Science:

• Molecular Biology
• Structural Biology
• Genetics

Background:

• The origin recognition complex (ORC) is crucial for DNA replication initiation, recognizing and marking specific DNA sites.
• The precise molecular mechanisms governing human ORC activation for DNA binding are not fully understood.

Purpose of the Study:

• To elucidate the structural basis of human ORC autoinhibition and activation.
• To characterize the conformations of human ORC1-5 and ORC2-5 assemblies.

Main Methods:

• X-ray crystallography
• Structural analysis of protein complexes
• Biophysical characterization

Main Results:

• Human ORC2-5 adopts a tightly autoinhibited state, with ORC2's winged-helix domain blocking the DNA-binding channel.
• ORC1 binding partially relieves autoinhibition by remodeling ORC2-WHD, allowing for a more dynamic, yet still inhibited, structure.
• The AAA+ domain of ORC1 displays flexibility, sampling conformations from inactive to potentially active states.

Conclusions:

• These findings provide detailed insights into the regulation of human ORC autoinhibition.
• The study illuminates mechanisms underlying ORC activation for DNA binding during replication initiation.