TAF1B is a TFIIB-like general transcription factor component of the human SL1/TIF-IB complex that plays a critical role in RNA polymerase I (Pol I) transcription initiation 1. As a subunit of the Pol I basal transcription machinery, TAF1B contains predicted amino-terminal zinc ribbon and cyclin-like fold domains characteristic of TFIIB-related proteins 1. TAF1B functions in multiple initiation steps: it binds ribosomal DNA promoters and mediates Pol I recruitment to rRNA genes as a component of SL1, and also has an essential postpolymerase recruitment role in preinitiation complex assembly 1. This represents a conserved transcription initiation mechanism paralleling Pol II and III systems 1. Clinically, TAF1B has emerged as a disease-relevant gene in multiple contexts. TAF1B mutations occur with very high frequency (82%) in microsatellite-instable colorectal carcinomas, with evidence suggesting these mutations are selected during tumorigenesis 2. Additionally, TAF1B was identified as a key FOXO3-associated gene in a prognostic model for hepatocellular carcinoma, where elevated TAF1B expression correlates with poor prognosis 3. TAF1B methylation at cg08035323 shows heritable DNA methylation changes associated with blood pressure regulation 4, suggesting broader physiological functions beyond rRNA synthesis.