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RNA Polymerase III Transcription Initiation

Stable Identifier
Homo sapiens
Locations in the PathwayBrowser

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).

Some promoters combine elements from type 2 and 3 promoters. For example, the S. cerevisiae 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 S. pombe, nearly all tRNA and 5S genes contain a TATA box in addition to gene-internal elements, and the TATA box is required for transcription.

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