The properties of chimeric picornavirus IRESes show that discrimination between internal translation initiation sites is influenced by the identity of the IRES and not just the context of the AUG codon
The properties of chimeric picornavirus IRESes show that discrimination between internal translation initiation sites is influenced by the identity of the IRES and not just the context of the AUG codon
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DOI：
10.1017/s1355838299982158
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发表时间：
1999-06-01
期刊：
影响因子：
4.5
通讯作者：
Jackson, RJ
中科院分区：
文献类型：
--
作者：
Ohlmann, T;Jackson, RJ
小RNA病毒的内部核糖体进入片段（IRES）由类似于450 nt的5'非翻译区组成，终止于3'端；具有类似于25 nt的元件，由绝对保守的UUUC基序组成，随后是更可变的富含嘧啶的片段和贫G间隔区，最后是AUG三联体，被认为是实际的核糖体进入位点。进入该位点后的事件在小核糖核酸病毒之间有所不同：在脑心肌炎病毒（EMCV）中，几乎所有核糖体都在此位点启动翻译（AUG-11）；在口蹄疫病毒 (FMDV) 中，三分之一的核糖体起始于该 AUG（实验室位点），其余的则起始于下一个 AUG 84 nt 下游（Lb 位点）；在脊髓灰质炎病毒 (PV) 中，IRES 3' 端的 AUG（PV 1 型中的 nt 586）被认为是沉默进入位点，所有核糖体在下一个 AUG 下游（nt 743）处启动翻译。为了研究是什么决定了这种不同的行为，在保守的 UUUC 基序上进行了交叉构建了嵌合体：IRES 的主体、该 UUUC 基序的上游序列来自一个物种，而下游序列来自另一个物种。当FMDV或PV IRESes的主体被EMCV的主体取代时，上游AUG、FMDV的实验室位点和PV的(586)AUG的起始绝对频率和相对频率分别显着增加。相反，当EMCV IRES的主体被PV的主体取代时，在三个AUG处没有偏好地发生启动：正常位点(AUG-11)、位于上游8nt的AUG-10和位于下游12nt的AUG-12。因此，尽管 IRES 3' 端的 AUG 背景可能会影响：如通过改善 PV 的 (586)AUG 背景所示，该位点的起始频率，但核糖体的行为也高度依赖于上游 IRES 的性质。使用 EMCV IRES，以具有启动能力的方式将核糖体递送至该 AUG 特别高效且准确。
The internal ribosome entry segment (IRES) of picornaviruses consists of similar to 450 nt of 5'-untranslated region, terminating at the 3' end;with an similar to 25 nt element consisting of an absolutely conserved UUUC motif followed by a more variable pyrimidine-rich tract and G-poor spacer, and finally an AUG triplet, which is considered to be the actual ribosome entry site. Events following entry at this site differ among picornaviruses: in encephalomyocarditis virus (EMCV) virtually all ribosomes initiate translation at this-site (AUG-11); in foot-and-mouth-disease virus (FMDV), one-third of the ribosomes initiate at this AUG (the Lab site), and the rest at the next AUG 84 nt downstream (Lb site); and in poliovirus (PV), the AUG at the 3' end of the IRES (at nt 586 in PV type 1) is considered to be a silent entry site, with all ribosomes initiating translation at the next AUG downstream (nt 743). To investigate what determines this different behavior, chimeras were constructed with a crossover at the conserved UUUC motif: the body of the IRES, the sequences upstream of,this UUUC motif, was derived from one species, and the downstream sequences from another. When the body of the FMDV or PV IRESes was replaced by that of EMCV, there was a marked increase in the absolute and relative frequency of initiation at the upstream AUG, the Lab site of FMDV and (586)AUG Of PV, respectively. In contrast, when the body of the EMCV IRES was replaced by that of PV, Initiation occurred with no preference at three AUGs: the normal site (AUG-11), AUG-10 situated 8 nt upstream, and AUG-12, which is 12 nt downstream. Thus although the context of the AUG at the 3' end of the IRES may influence: initiation frequency at this site, as was shown by improving the context, of (586)AUG of PV, the behavior of the ribosome is also highly dependent on the nature of the upstream IRES. Delivery of the ribosome to this AUG in an initiation-competent manner is particularly efficient and accurate with the EMCV IRES.