Fig. 7: A hypothetical model depicting how SPOP mutation impairs DNA replication and sensitizes cancer cells to ATR inhibition.

a SPOP-CUL3-RBX1 functions as an E3 ubiquitin ligase that binds to Geminin and catalyzes K27-linked poly-ubiquitination of Geminin at Lys100 and Lys127. b SPOP-dependent Geminin poly-ubiquitination blocks Cdt1 binding to MCM proteins. Poly-ubiquitination keeps the licensing-competent state in check and prevents DNA replication over-firing. c Cancer-associated SPOP mutations impair DNA replication surveillance and cause replication origin over-firing and re-replication. d SPOP mutations trigger replication catastrophe and cancer cell death upon ATR inhibition.