Twistnb is a DNA-dependent RNA polymerase that catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. Component of RNA polymerase I which synthesizes ribosomal RNA precursors through its association with RRN3/TIF-IA may be involved in recruitment of Pol I to rDNA promoters. This protein contains 2 potential nuclear localization signals in the C terminus and shares 72 % sequence identity with the mouse orthologs. Twistnb has highest expression in fetal lung, liver, and kidney, and low expression in all adult tissues.