MXD4 (MAX Dimerization Protein 4) is a transcriptional repressor that functions as a MYC antagonist by forming sequence-specific DNA-binding complexes with MAX 12. The protein recognizes the core DNA sequence 5'-CAC[GA]TG-3' and suppresses MYC-dependent gene expression and cell transformation 13. MXD4 belongs to the extended Myc Network, where it opposes MYC functions by competing for MAX binding, thereby regulating proliferation, metabolism, and cell survival 3. In acute myeloid leukemia, MXD4 acts as a tumor suppressor whose expression is suppressed by the UHRF1-SAP30 axis and METTL16-mediated mRNA instability, leading to MYC pathway activation and leukemogenesis 12. MXD4 also regulates normal tissue homeostasis, controlling keratinocyte precursor fate in human epidermis and promoting CD8+ T-cell memory formation 45. Additionally, MXD4 contributes to T-cell survival through OX40 engagement-mediated protein stabilization 6. Dysregulation of MXD4 through fusion proteins (MAD::NUT fusions) defines a distinct class of sarcomas separate from NUT carcinoma 7. The protein's function as a MYC antagonist makes it crucial for preventing aberrant cell proliferation and maintaining cellular homeostasis.