Multi-Faceted Regulation of the Sumoylation of the Sgs1 DNA Helicase in Genome Maintenance
Mutchler, Ashley S.
To minimize DNA damage-induced genome instability and cancer formation, the DNA repair system requires proper regulation to adjust its efficiency and actions. Sumoylation is emerging as an important regulatory means for many forms DNA repair pathways, including homologous recombination (HR) repair. However, how HR proteins are dynamically sumoylated to modulate their functions remains poorly understood. The Sgs1-Top3-Rmi1 (STR) complex in budding yeast and its human counterpart BLM-Topo IIIa-RMI1-RMI2 (BTRR) play pivotal roles in genome maintenance. They affect multiple steps during HR. We recently reported that all three STR subunits are sumoylated and this requires the SUMO E3 ligase, Nse2 (aka Mms21), a subunit of the Smc5/6 complex. Further, STR sumoylation positively influence HJ removal as sumoylation promotes subunit interaction and recruitment to DNA repair foci. Our recent effort addresses the factors that directly promote STR sumoylation using a combination of in vitro sumoylation systems and cellular assays. We demonstrated that DNA binding per se enhances Sgs1 sumoylation in vitro, providing one mechanism for the observed HJ requirement in STR sumoylation in cells. In addition, we show that a scaffold protein Esc2 stimulates Mms21-mediated STR sumoylation in vivo and in vitro. Esc2’s action requires two distinct domains. Esc2 stimulates STR sumoylation through its C-terminal SLD2 domain binding to the backside of SUMO E2. A separate effect is mediated by the Esc2 mid-region (MR). Interestingly, though Esc2-MR binds HJ DNA, its stimulation of Sgs1 sumoylation is separable from this DNA binding activity, suggesting a dual role of the Esc2-MR domain. Consistent with the in vitro data, cellular results provided evidence that Sgs1 function and sumoylation are positively affected by the two Esc2 domains. In summary, our finding defined multiple stimulatory elements that render efficient Sgs1 sumoylation in promoting its functions, thus advancing our understanding of how sumoylation regulates DNA repair and genome maintenance.
DNA helicase, genome maintenance
Xue, X., Li, S., Mutchler, A., Zhu, X., So, S., Epps, J., Guan, D., & Zhao, X. (2023). Multi-faceted regulation of the sumoylation of the Sgs1 DNA helicase in genome maintenance. Poster presented at the Health Scholar Showcase, Translational Health Research Center, San Marcos, Texas.