蝦白點症病毒三種結構蛋白質基因(wssv311, 364和395)轉錄分析與基因wssv395轉譯機轉分析之研究

蝦白點症之三種結構蛋白質基因wssv311, wssv364與wssv395已完成定序，並分析其基因結構。此三種基因之轉錄本轉錄起始點位置，鑑定此三基因中僅有wssv364具有TATA box序列與Inr保守性序列；在wssv395三端加聚腺嘌呤上游第14 bp位有AAUAAA加聚腺嘌呤信號；在其下游序列11 bp處，發現一由7個核苷酸鎖組成之保守序列UUUUAUU，其可能參與加聚腺嘌呤作用之調控。藉由RACE與北方轉印法(northern blotting)可推測wssv396, wssv395與wssv394具有相同的轉錄起始點並共用同一轉錄本，並由試管內轉錄和轉譯證實。此轉錄本之第二開放譯讀區(open reading frame; ORF)則利用核糖體內部進入位點(internal ribosomal entry site; IRES)進行轉譯作用，即wssv395可不經由5端冠端結構獨立進行轉譯作用 (5’ cap-independent translation)，預測wssv395之5端非轉譯區域(untranslated region)的二級結構，可觀察到其具有六個莖環結構(stem-loop structures)，推測此二級結構可與轉譯有關之蛋白質結合，使得核糖體可在此進行轉譯作用。

關鍵字

蝦白點症病毒；結構蛋白質基因；核糖體內部進入位點

並列摘要

Three WSSV (white spot syndrome virus) structural protein genes (wssv311, 364 and 395) were identified, sequenced and analyzed from the predicted open reading frame from the Taiwan isolate. Comparison transcriptional initiation sites of these genes, only wssv364 gene contains TATA element and Inr-like mostif. Analysis of polyadenylation addition site of wssv395 gene revealed that the AAUAAA polyadenylation signal sequence was at a site 14 nt upstream of the polyadenylation addition site and the UUUUAUU consensus sequence was located at 11 nt downstream of it. This motif may joint the regulation of polyadenylation. By RACE, Northern blot, and RT-PCR analysis, this study confirmed a tricistronic transcript that contains three structural protein genes, wssv394, wssv395, and wssv396. In vitro transcription and translation assays of tricistronic transcript showed that three proteins were translated by one transcript. And wssv395 gene was translated by internal ribosome entry by showing that second ORF translation is cap-independent translation. The secondary structure of 5’UTR of wssv395 gene was predicted and shown IRES-like secondary structure which consists of six stem-loops 283 nt upstream of the start codon.

並列關鍵字

WSSV ； structural protein gene ； IRES

參考文獻

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蝦白點症病毒三種結構蛋白質基因(wssv311, 364和395)轉錄分析與基因wssv395轉譯機轉分析之研究

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