XPO1 sustains the turnover of proteins modulating DNA damage repair. A, Representative immunoblot of indicated DNA damage repair proteins in OCI-Ly1 cells exposed to vehicle, selinexor (1 μmol/L), etoposide (3 μmol/L), or their combination for 24 hours. B, Representative immunoblot of indicated DNA damage repair proteins in P493–6 B-cells after induction of MYC (30 minutes after doxycycline withdrawal) and exposure to vehicle or selinexor (1 μmol/L) for 24 hours. C, Expression levels of transcripts encoding for DNA damage repair protein in OCI-Ly1 cells exposed to vehicle, selinexor (1 μmol/L), etoposide (3 μmol/L), or their combination for 6 hours. D and E, Representative immunoblots (D) of cycloheximide (CHX) chase assay of CHEK1, RAD51, and WEE1 (and actin as control) in OCI-Ly1 cells exposed to vehicle or selinexor (1 μmol/L) for the indicated times. The relative amount of each protein compared with β-actin was quantified by densitometry and plotted with respect to time (E). The protein to β-actin level at baseline was defined as 100%. F, Immunoblots showing CHEK1, RAD51, and WEE1 (and actin as control) protein levels in the newly synthesized fraction (AHA-pulldown) over total protein abundance (input) in OCI-Ly1 cells exposed to vehicle, selinexor (1 μmol/L), etoposide (3 μmol/L), or their combination for 6 hours.