Updated project metadata. Our CRISPR-based pharmacogenomic screening identified the E3 ubiquitin ligase Herc1 as a key modulator of sensitivity to cytarabine (Ara-C) chemotherapy in the MLL/AF9 (MA) mouse AML model both in vitro and in vivo. To identify the intracellular proteins whose abundance is modulated by Herc1, we performed comparative LC-MS3 analysis of in vitro-cultured MA mouse AML cells that were transduced with either a small-guide RNA targeting Herc1 (i.e., CRISPR-mediated Herc1-knockout) or a control non-targeting small-guide RNA, at steady state or after brief exposure to Ara-C (200 nMol for 6 hours).