7-14 nt. Backtracking of Pol II complex on the HIV-1 template leading to elongation arrest

RNA Pol II arrest is believed to be a result of irreversible backsliding of the enzyme by ~7-14 nucleotides. It is suggested that, arrest leads to extrusion of displaced transcripts 3'-end through the small pore near the Mg2+ ion. Pol II arrest may lead to abortive termination of elongation due to irreversible trapping of the 3'-end of the displaced transcript in the pore (reviewed by Shilatifard et al., 2003).

RNA聚合酶II的阻滞被认为是由该酶约7-14个核苷酸不可逆回退所致。有研究表明，阻滞会导致位移转录本的3'-端通过靠近Mg2+离子的微小孔隙被挤出。RNA聚合酶II的阻滞可能由于位移转录本3'-端在孔隙中不可逆地被捕获而导致延伸的终止（参见Shilatifard等人，2003年的综述）。