Kash S F, Innis J W, Jackson A U, Kellems R E
Institute for Molecular Genetics, Baylor College of Medicine, Houston, Texas 77030.
Mol Cell Biol. 1993 May;13(5):2718-29. doi: 10.1128/mcb.13.5.2718-2729.1993.
Transcription arrest plays a role in regulating the expression of a number of genes, including the murine adenosine deaminase (ADA) gene. We have previously identified two prominent arrest sites at the 5' end of the ADA gene: one in the first exon and one in the first intron (J. W. Innis and R. E. Kellems, Mol. Cell. Biol. 11:5398-5409, 1991). Here we report the functional characterization of the intron 1 arrest site, located 137 to 145 nucleotides downstream of the cap site. We have determined, using gel filtration, that the intron 1 arrest site is a stable RNA polymerase II pause site and that the transcription elongation factor SII promotes read-through at this site. Additionally, the sequence determinants for the pause are located within a 37-bp fragment encompassing this site (+123 to +158) and can direct transcription arrest in an orientation-dependent manner in the context of the ADA and adenovirus major late promoters. Specific point mutations in this region increase or decrease the relative pausing efficiency. We also show that the sequence determinants for transcription arrest can function when placed an additional 104 bp downstream of their natural position.
转录终止在调控包括小鼠腺苷脱氨酶（ADA）基因在内的许多基因的表达中发挥作用。我们之前已在ADA基因的5'端鉴定出两个显著的终止位点：一个在第一个外显子中，另一个在第一个内含子中（J. W. Innis和R. E. Kellems，《分子与细胞生物学》11:5398 - 5409，1991）。在此我们报告位于帽位点下游137至145个核苷酸处的内含子1终止位点的功能特性。我们通过凝胶过滤确定，内含子1终止位点是一个稳定的RNA聚合酶II暂停位点，并且转录延伸因子SII促进在此位点的通读。此外，暂停的序列决定因素位于一个包含该位点（+123至+158）的37碱基对片段内，并且在ADA和腺病毒主要晚期启动子的背景下能够以方向依赖的方式指导转录终止。该区域的特定点突变会增加或降低相对暂停效率。我们还表明，转录终止的序列决定因素在其天然位置下游额外104碱基对处放置时仍能发挥作用。
