ARID4B is an AT-rich interaction domain protein that functions as both a transcriptional repressor and coactivator with context-dependent roles in gene regulation. As a repressor, it functions within the Sin3A corepressor complex to mediate chr1 modifications 1. ARID4B contains an interdigitated double Tudor domain with DNA-binding activity, though with weaker DNA affinity than its homolog ARID4A due to specific residue differences affecting charge distribution 2. In normal physiology, ARID4B co-regulates spermatogenesis with ARID4A and participates in epigenetic modifications at imprinting centers. In cancer biology, ARID4B exhibits predominantly oncogenic functions across multiple malignancies. In glioblastoma, ARID4B overexpression correlates with WHO grade IV tumors, and its knockdown suppresses proliferation via PI3K/AKT pathway inhibition and induces G1 arrest 3. Similarly, in hepatocellular carcinoma, high ARID4B scores independently predict poor disease-free and overall survival, with knockdown suppressing PI3K/AKT signaling and cell invasion 4. In breast cancer, ARID4B expression promotes metastatic progression and predicts distant metastasis-free survival in ER+ tumors 5. Conversely, in prostate cancer, ARID4A and ARID4B downregulation associates with high Gleason scores and poor prognosis, suggesting tumor suppressor roles 6. In bladder cancer, miR-17-5p suppresses ARID4B expression to promote invasion 7. Overexpression of ARID4B isoforms induces G1 cell cycle arrest 8, indicating complex regulatory mechanisms dependent on tissue and genetic context.