TAF5L (TATA-box binding protein associated factor 5 like) functions as a component of the SAGA complex, a 20-subunit transcriptional coactivator 1. As part of the PCAF/SAGA complex, TAF5L participates in histone acetylation, particularly H3K9ac deposition, and regulates transcription through recruitment of the MYC transcriptional network 2. In embryonic stem cells, TAF5L and its paralog TAF6L maintain self-renewal by transcriptionally activating c-Myc and Oct4, orchestrating gene expression programs essential for pluripotency maintenance 2. TAF5L serves as a critical regulator of hematopoiesis; loss of Taf5l in hematopoietic stem and progenitor cells strongly inhibits blood production in vivo, causing accumulation of immature hematopoietic cells and upregulation of interferon pathway genes 34. Pathologically, TAF5L dysregulation associates with multiple diseases: its expression correlates with HIV replication in people living with HIV 5, it functions as a hub protein in hepatocellular carcinoma networks where USP22 upregulation occurs 6, and genetic variants show marginal associations with type 1 diabetes susceptibility 7. Recent evidence demonstrates TAF5L expression enhances CD8+ regulatory T cell stability and suppressive function 8, indicating roles in immune regulation beyond hematopoiesis.