TOP2B cooperates with ATRX to resolve G-quadruplexes and maintain replication fork stability in glioma

ATRX is a chromatin remodeling protein that maintains genomic stability by resolving G-quadruplex (G4) DNA structure. However, the details of resolving G4 by ATRX remain unclear. Here, we unveil that TOP2B and ATRX collaborate to maintain genomic stability by regulating G4. ATRX deficiency causes the accumulation of G4 and increases cells' reliance on TOP2B to resolve G4 structures and maintain replication fork stability. CX-5461, as a TOP2B poison, stabilizes G4 by trapping TOP2B on DNA as well as inhibiting the formation of the ATRX-TOP2B complex and its recruitment to G4 sites. CX-5461 treatment resulted in the entrapment of TOP2B and the subsequent hyperaccumulation of G4 in ATRX-deficient glioma cells, ultimately leading to genomic instability and cell death. Furthermore, we found that YTHDF3 promotes ATRX protein synthesis through m6A modification. Our findings suggest that targeting TOP2B with CX-5461 has therapeutic potential for ATRX-deficient gliomas, offering a promising direction for future treatment strategies. Overall design: To investigate the cooperative function of ATRX/TOP2B complex in the DNA replication and DNA damage response, we established U87MG cell lines in which each target gene has been knocked down by siRNA.