Fig. 2

BLM drives ALT by promoting APB formation and BIR. A. The BTR complex and TRF2 or POT1 colocalize on telomeres and promote APB formation in a PML-dependent manner (a). The SUMO-SIM interactions of telomeres with BLM and RAD52 can induce the formation of nuclear structures via LLPS (b). B. BLM is required for the initiation of RAD52-dependent BIR through 5’ to 3’ end resection (a). In RAD52-independent BIR, BLM is also responsible for telomere synthesis and C-circle formation (b). The BTR complex is essential for the dissolution of recombination intermediates, resulting in POLD3-dependent ALT telomere extension