Yu K, Elder R T
Department of Molecular Genetics and Cell Biology, University of Chicago, Illinois 60637.
Mol Cell Biol. 1989 Sep;9(9):3667-78. doi: 10.1128/mcb.9.9.3667-3678.1989.
The major transcript of the yeast transposable element Ty1 has its 5' end in one delta and the 3' end in the opposite delta, the direct repeats of about 335 base pairs (bp) at each end of the element. The transcriptional initiation signals of the Ty-D15 element that give rise to this transcript were found to have a number of unusual characteristics. The 5' delta by itself, which contained the initiation site for Ty transcription, gave no detectable transcription. A region internal to the transcript in a translated part of the element and about 140 bp downstream of the 5' delta was essential for initiation of the major Ty transcript. This internal activating region (IAR) had several interesting properties. When the portion of the delta upstream of the initiation site was replaced with DNA fragments that did not by themselves act as promoters, initiation directed by the IAR still occurred at about the same position, 200 to 400 bp upstream of the IAR. If fragments containing the IAR were inverted, transcription could still occur. When 468 or 636 bp was inserted between the delta and the IAR, initiations occurred near the normal delta initiation site and in the inserted DNA. Therefore, the location and properties of transcription signals for Ty-D15 differ considerably from those expected for a yeast gene transcribed by RNA polymerase II.
酵母转座因子Ty1的主要转录本，其5'端位于一个δ元件中，3'端位于相对的δ元件中，该元件两端有大约335个碱基对（bp）的同向重复序列。发现产生此转录本的Ty-D15元件的转录起始信号具有许多不寻常的特征。单独的5'δ元件，其中包含Ty转录的起始位点，未检测到转录。在该元件翻译部分的转录本内部且在5'δ元件下游约140bp处的一个区域，对于主要Ty转录本的起始至关重要。这个内部激活区域（IAR）具有几个有趣的特性。当起始位点上游的δ元件部分被本身不作为启动子的DNA片段取代时，由IAR指导的起始仍在IAR上游约200至400bp的大致相同位置发生。如果包含IAR的片段被颠倒，转录仍可发生。当在δ元件和IAR之间插入468或636bp时，起始在正常的δ元件起始位点附近和插入的DNA中发生。因此，Ty-D15转录信号的位置和特性与RNA聚合酶II转录的酵母基因预期的位置和特性有很大不同。
