PathwayStep189 PathwayStep193 PathwayStep197 RNA Polymerase III Transcription Initiation From Type 3 Promoter RNA Polymerase III Transcription Initiation From Type 1 Promoter RNA Polymerase III Transcription Initiation From Type 2 Promoter RNA Polymerase III Transcription Initiation Authored: Hernandez, N, 2003-09-11 07:42:29 Edited: Joshi-Tope, G, 0000-00-00 00:00:00 Pubmed2308839 Pubmed2752422 Pubmed6947245 Pubmed7312050 Pubmed7357599 Pubmed7357604 Reactome Database ID Release 4376046 Reactome, http://www.reactome.org ReactomeREACT_281 There are three basic types of RNA polymerase III promoters. The three types of RNA polymerase III promoters are known as type 1, type 2, and type 3 promoters. Type 1 promoters are found in the 5S genes and consist of a gene-internal element called the internal control region (ICR), that is subdivided into A block, intermediate element, and C block (Bogenhagen, 1985; Sakonju et al., 1980). Type 2 promoters are found in tRNA genes, Adenovirus 2 VAI gene, and other genes (Galli et al., 1981; Sharp et al., 1981). These promoters consists of two gene-internal elements called the A and the B boxes. Type 3 promoters consist of a distal sequence element (DSE) that serves as an enhancer, a proximal sequence element (PSE), and a TATA box (Baer et al., 1989; Lobo and Hernandez, 1989). <p>Some promoters combine elements from type 2 and 3 promoters. For example, the <i>S. cerevisiae</i> U6 promoter, also shown in the figure, contains the TATA box typical of type 3 promoters and the A and B boxes typical of type 2 promoters. Moreover, in <i>S. pombe</i>, nearly all tRNA and 5S genes contain a TATA box in addition to gene-internal elements, and the TATA box is required for transcription.