Domenjoud L, Gallinaro H, Kister L, Meyer S, Jacob M
Laboratoire de Génétique Moléculaire des Eucaryotes du Centre National de la Recherche Scientifique, Unité 184, Faculté de Médecine, Strasbourg, France.
Mol Cell Biol. 1991 Sep;11(9):4581-90. doi: 10.1128/mcb.11.9.4581-4590.1991.
The first intron of the early region 3 from adenovirus type 2 contains a cryptic 5' splice site, Dcr1, 74 nucleotides downstream from the natural site D1. The cryptic site can be activated when the natural site is inactivated by mutagenesis. To investigate the basis for selection between a natural and a cryptic 5' splice site, we searched for cis-acting elements responsible for the exclusive selection of the natural site. We show that both the relative intrinsic strength of the sites and the sequence context affect the selection. A 120-nucleotide segment located at the 3' end of exon 1 enhances splicing at the proximal site D1; in its absence the two sites are used according to their strength. Thus, three cis-acting elements are involved in the silencing of the cryptic site: the sequence of D1, the sequence of Dcr1, and an upstream exonic sequence. We show that the exonic element folds, in solution, into a 113-nucleotide-long stem-loop structure. We propose that this potential stem-loop structure which is located 6 nucleotides upstream of the exon 1-intron junction is responsible for the preferential use of the natural 5' splice site.
2型腺病毒早期区域3的第一个内含子包含一个隐蔽的5'剪接位点Dcr1，它位于天然位点D1下游74个核苷酸处。当天然位点通过诱变失活时，隐蔽位点可以被激活。为了研究在天然和隐蔽5'剪接位点之间进行选择的基础，我们寻找负责天然位点排他性选择的顺式作用元件。我们表明，位点的相对内在强度和序列上下文都会影响选择。位于外显子1 3'端的一个120个核苷酸的片段增强了近端位点D1的剪接；在其缺失的情况下，这两个位点根据其强度被使用。因此，三个顺式作用元件参与了隐蔽位点的沉默：D1的序列、Dcr1的序列和一个上游外显子序列。我们表明，外显子元件在溶液中折叠成一个113个核苷酸长的茎环结构。我们提出，这个位于外显子1-内含子连接处上游6个核苷酸处的潜在茎环结构负责天然5'剪接位点的优先使用。
