Burton Z F, Ortolan L G, Greenblatt J
EMBO J. 1986 Nov;5(11):2923-30. doi: 10.1002/j.1460-2075.1986.tb04588.x.
Extracts prepared from HeLa cell nuclei are inactivated for accurate transcription from the adenovirus 2 major late promoter (Ad2 MLP) by repeated passage over a column containing immobilized calf thymus RNA polymerase II. The capacity for accurate transcription is restored to these extracts by a fraction that is eluted from the RNA polymerase II column with 0.5 M KC1. This fraction contains RNA polymerase II-associating proteins (RAPs). RAPs are not required for the formation of a stable, promoter-associated pre-initiation complex. However, at least one RAP is required for the formation of the first phosphodiester bond at the Ad2 MLP, both when initiation depends only on the TATAAA box, and when initiation is stimulated by the upstream sequence of the promoter. Initiation occurs approximately 1 min after the addition of RAPs to initiation complexes formed in the absence of RAPs. Therefore, the RAP(s) that is an RNA polymerase II initiation factor functions late in the initiation pathway to convert a stable preinitiation complex to an initiation-competent complex.
从HeLa细胞核制备的提取物，通过在含有固定化小牛胸腺RNA聚合酶II的柱上反复过柱，会失去从腺病毒2主要晚期启动子（Ad2 MLP）进行准确转录的能力。用0.5 M KCl从RNA聚合酶II柱上洗脱下来的一个组分可使这些提取物恢复准确转录的能力。该组分含有与RNA聚合酶II相关的蛋白质（RAPs）。形成稳定的、与启动子相关的预起始复合物不需要RAPs。然而，当起始仅依赖于TATAAA框时，以及当起始受到启动子上游序列刺激时，在Ad2 MLP处形成第一个磷酸二酯键至少需要一种RAP。在向无RAPs时形成的起始复合物中添加RAPs后约1分钟发生起始。因此，作为RNA聚合酶II起始因子的RAP在起始途径后期起作用，将稳定的预起始复合物转化为具有起始能力的复合物。
