The t(7;12) AML subtype in pediatric patients is associated with upregulation of homeodomain protein MNX1 as the initiating event for leukemogenesis. In this study, we investigated the downstream targets of MNX1 and their relationship to the histone modifications previously observed to be mediated by MNX1. Using a comprehensive approach combining TMT mass spectrometry, RNA-Seq, qPCR, ACT-seq, ATAC-seq, and ChIP-qPCR, we identified PBXIP1 along with its associated pioneer transcription factor PBX1 and PBX4 as downstream targets of MNX1. MNX1 binding to the Pbx1 promoter triggered its transcriptional activation, which was associated with an increase in the activating histone mark H3K4me3 and a decrease in the repressive mark H3K27me3 at the promoter site. Notably, despite the transient nature of MNX1’s promoter interaction, these histone marks persisted, suggesting a “hit-and-run” epigenetic remodeling mechanism. Enrichment of PBX motifs within MNX1-induced H3K4me1, H3K4me3, and ATAC-seq peaks underscores the pivotal role of the PBX family in MNX1-mediated chromatin dynamics. This was further confirmed by showing that MNX1-induced PBX1 expression could be downregulated using the Sinefungin inhibitor, a pan-methyltransferase inhibitor, that also prevent leukemia development. Our findings provide insights into how MNX1-driven epigenetic modifications are connected to its downstream targets and may offer new avenues for therapeutic intervention in t(7;12) AML.