Accurate transcription initiation on TATA-containing class II genes involves the ordered assembly of RNA polymerase II (POLR2A; MIM 180660) and several general initiation factors (summarized by DeJong and Roeder, 1993 [PubMed 8224848]). One of these factors is TFIIA, which when purified from HeLa extracts consists of 35-, 19-, and 12-kD subunits.[supplied by OMIM, Jul 2010].