Kur J, Hradecna Z, Hasan N, Szybalski W
McArdle Laboratory for Cancer Research, University of Wisconsin, Madison 53706.
Virology. 1990 Jun;176(2):629-32. doi: 10.1016/0042-6822(90)90034-o.
For antitermination of transcription from the late p'R promoter of phage lambda, a cis-acting qut sequence, which overlaps with p'R, is required, together with the product of lambda gene Q. Using our BspMI-mediated multicycle technique for generation of precise deletions, we have confirmed that deletions removing DNA downstream of +18 bp (counted from the p'R-controlled transcriptional start point s'R = +1) do not affect the efficiency of qut antitermination; at the same time we found that deleting one more bp (shifting the right-hand boundary to bp +17) reduces antitermination by only 20%. Deleting another 5 or 6 bp (+11 or +12 bp right-hand qut boundary), decreases antitermination by about 80%. These deletions reduce the 9/10-bp-direct repeat (5'-TGGGT(A or T)AATT)2 in qut to only the five italicized bp. Similar strong reduction in antitermination (by about 68%) was obtained with +16 bp qut boundaries, in constructs which also contained 2- or 3-bp insertions between bp +11 and +12 or between +12 and +13. Since the latter deletions retain only 5/10 bp of the direct repeat, it appears that antitermination is dependent on the length and intactness of the direct repeat.
对于噬菌体λ晚期p'R启动子转录的抗终止作用，需要一个与p'R重叠的顺式作用qut序列，以及λ基因Q的产物。利用我们的BspMI介导的多轮技术来产生精确缺失，我们已经证实，缺失从+18 bp下游（从p'R控制的转录起始点s'R = +1开始计数）的DNA不会影响qut抗终止的效率；同时我们发现再多缺失一个bp（将右手边界移至bp +17）只会使抗终止作用降低20%。再缺失另外5或6 bp（qut右手边界为+11或+12 bp），会使抗终止作用降低约80%。这些缺失将qut中的9/10-bp直接重复序列（5'-TGGGT(A或T)AATT）2减少到仅五个斜体bp。在bp +11和+12之间或+12和+13之间还包含2或3 bp插入的构建体中，对于+16 bp的qut边界，也获得了类似的抗终止作用的强烈降低（约68%）。由于后一种缺失仅保留了直接重复序列的5/10 bp，因此似乎抗终止作用取决于直接重复序列的长度和完整性。
