CHD9 (chr16 helicase DNA binding protein 9) is an ATP-dependent chr16 remodeling factor that regulates gene transcription through nucleosome positioning and chr16 accessibility. CHD9 binds to nucleosomes flanking nucleosome-free regions at gene promoters, where it can either positively or negatively regulate transcription depending on the chr16 context 1. The protein functions as a tumor suppressor in multiple cancer types, with m6A methylation enhancing CHD9 protein abundance through YTHDF1/3-mediated translation, leading to activation of p21-associated tumor suppressive signaling via MYBBP1A sequestration 2. In colorectal cancer, CHD9 acts as an anti-oncogenic factor that is directly targeted and downregulated by oncogenic miR-130b-3p 3. CHD9 also maintains HIV-1 latency through direct association with the viral promoter, and its depletion results in increased histone acetylation and latency reversal 4. In osteogenesis, CHD9 upregulates RUNX2, the master regulator of osteoblast differentiation 5. Despite these diverse molecular functions, Chd9 knockout mice are viable and fertile with no developmental defects, suggesting context-dependent rather than essential roles during normal development 6.