EXO1, MRE11, CtIP, and MUS81 depletion does not affect stalled fork processing. (A) Statistical analysis of IdU tracts from U-2 OS cells depleted for the indicated proteins in the presence of 4 mM HU. (B) Representative IdU tracts in control, RECQ1-, MRE11-, or RECQ1/MRE11-codepleted U-2 OS cells (out of 2 repeats). (top) Expression of RECQ1 and MRE11 after siRNA knockdown. (C) Representative IdU tracts in control, RECQ1-, EXO1-, or RECQ1/EXO1-codepleted U-2 OS cells (out of 2 repeats). (top) Expression of RECQ1 and EXO1 after siRNA knockdown. (D) Representative IdU tracts in control, RECQ1-, CtIP-, or RECQ1/CtIP-codepleted U-2 OS cells (out of 2 repeats). (top) Expression of RECQ1 and CtIP after siRNA knockdown. (E) Representative IdU tracts in Luc-, RECQ1-, MUS81-, or RECQ1/MUS81-codepleted U-2 OS cells in the presence of HU (out of 2 repeats). (left) Expression of RECQ1 and MUS81 after shRNA knockdown. n ≥ 300 tracts scored for each dataset shown in A–E.