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. 2000 Oct 15;14(20):2650–2663. doi: 10.1101/gad.836400

Figure 9.

Figure 9

Model of the initiation complexes formed on tRNA-type and U6-type promoters. The upper panel shows a tRNA-type promoter with the gene internal A and B box promoter elements recruiting TFIIIC, which in turn can recruit through protein–protein contacts the TFIIIB components TBP, hBRF, and hB′′. The dotted line separating TBP and hBRF indicates that these two factors are tightly associated with each other. The solid line separating hB′′ from the TBP–hBRF complex indicates that hB′′ is only weakly associated with the rest of the complex. The lower panel shows that for the human U6 gene, the external PSE and TATA box core promoter elements recruit SNAPc and the TFIIIB component TBP, respectively. The binding of these factors probably allows the recruitment of hB′′ and a TFIIIB component specific for PSE-containing RNA polymerase III promoters, hBRFU. The solid lines separating TBP, hBRFU, and hB′′ indicate that in this case, the TFIIIB components are either not associated or only weakly associated with each other.