Abstract
The Smc5-6 complex is required for the maintenance of genome integrity through its functions in DNA repair and chromosome biogenesis. However, the specific mode of action of Smc5 and Smc6 in these processes remains largely unknown. We previously showed that individual components of the Smc5-Smc6 complex bind strongly to DNA as monomers, despite the absence of a canonical DNA-binding domain (DBD) in these proteins. How heterodimerization of Smc5-6 affects its binding to DNA, and which parts of the SMC molecules confer DNA-binding activity is not known at present. To address this knowledge gap, we characterized the functional domains of the Smc5-6 heterodimer and identify two DBDs in each SMC molecule. The first DBD is located within the SMC hinge region and its adjacent coiled-coil arms, while the second is found in the conserved ATPase head domain. These DBDs can independently recapitulate the substrate preference of the full-length Smc5 and Smc6 proteins. We also show that heterodimerization of full-length proteins specifically increases the affinity of the resulting complex for double-stranded DNA substrates. Collectively, our findings provide critical insights into the structural requirements for effective binding of the Smc5-6 complex to DNA repair substrates in vitro and in live cells.
Highlights
The Smc[5,6] complex is required for the maintenance of genome integrity through its functions in DNA repair and chromosome biogenesis
We previously showed that individual components of the Smc5-Smc[6] complex bind strongly to DNA as monomers, despite the absence of a canonical DNA-binding domain (DBD) in these proteins
To better understand how Smc[5] and Smc[6] function in vivo, we first wanted to determine the minimal regions of these proteins that are necessary and sufficient for binding to DNA
Summary
The Smc[5,6] complex is required for the maintenance of genome integrity through its functions in DNA repair and chromosome biogenesis. The cohesin and condensin complexes play key roles in sister chromatid cohesion and chromosome condensation, respectively[7,8] When DSBs are formed at the rDNA locus (in the nucleolus), homologous recombination is initiated but completion is prevented because Rad[52] is excluded from the nucleolus in a Smc5-6-dependent manner[14] This process relies on Rad[52] sumoylation, but does not seem to involve the sumo ligase activity of Nse2/Mms[21]. It is conceivable that Smc[5,6] proteins could maintain physical proximity between distinct chromosomal DNA regions via a non-topological mechanism, as recently observed with RecN, a bacterial SMC-like protein[21]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
