Table I. A human RAD6 interactome. N-terminally Flag-tagged RAD6A, RAD6B, KCMF1 and UBR2 were expressed in Flp-In 293 T-REx cells. Cells were lysed under non-denaturing conditions and Flag-tagged proteins isolated using Flag-M2 agarose beads. Immunopurified proteins were eluted, digested with trypsin, and analyzed by nLC-ESI-MS/MS. Each cell pool represents a biological replicate. Two technical replicates were conducted for each pool. Spectral counts for each protein identification are indicated. All proteins highlighted here were detected with a >95% confidence level (iProphet) and assigned a SAINT score >0.95. Previously reported and new RAD6 interactors are indicated at left. KCMF1 interactions shared with RAD6A/B, and UBR2-specific interactions are indicated at right. *Most of the identified RAD6 peptides do not distinguish between RAD6A and RAD6B; for clarity all RAD6 peptides were pooled (and listed under RAD6A) for the Flag-KCMF1 and Flag-UBR2 analyses.