We identified the chromatin-associated protein networks of CEBPA and SUMO2/3 in BLaER1 cells during the early stages of B-cell-to-macrophage transdifferentiation. Additionally, we studied the impact of SUMOylation inhibition (SUMOi) on CEBPA protein network composition utilizing the small molecule inhibitor ML-792. Protein network members were identified with Rapid Immunoprecipitation Mass spectrometry of Endogenous proteins (RIME) at 0, 6 and 24 h after induction of transdifferentiation in the absence and presence of ML-792. Mass spectrometry analyses were executed with high resolution mass spectrometry (LC-MS), using the Evosep One liquid chromatography system coupled to a hybrid trapped ion mobility quadrupole TOF mass spectrometer (Bruker timsTOF Pro) via a CaptiveSpray nano-electrospray ion source. High-confidence chromatome members were discriminated from background with SAINT analysis.