Sequences within the 5' untranslated region regulate the levels of a kinetoplast DNA topoisomerase mRNA during the cell cycle.
Sequences within the 5' untranslated region regulate the levels of a kinetoplast DNA topoisomerase mRNA during the cell cycle.
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5非翻译区内的序列在细胞周期中调节动质体 DNA 拓扑异构酶 mRNA 的水平。
DOI：
10.1128/mcb.16.12.6724
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发表时间：
1996
影响因子：
5.3
通讯作者：
Ray,DS
中科院分区：
文献类型：
--
作者：
Pasion,SG;Hines,JC;Ou,X;Mahmood,R;Ray,DS
锥虫的基因表达在很大程度上受转录后水平的调控，并通过将39个核苷酸的小外显子序列转剪接到mRNA的5′端，并在mRNA的3′端进行切割和多聚腺苷酸化，使mRNA前体成熟。为了初步鉴定锥虫DNA复制基因周期性表达的序列，我们在编码动基体DNA拓扑异构酶的TOP 2基因5′侧翼区定位了剪接受体位点，并对质粒编码的TOP 2基因进行了该区域的缺失分析。5′非翻译区（UTR）内的区块缺失确定了两个负责mRNA周期性积累的区域（−608至−388和−387至−186）。这些序列中的一个或另一个的缺失对mRNA的周期性表达没有影响，而两个区域的缺失导致mRNA在整个细胞周期中的组成型表达。将这些序列亚克隆到缺乏TOP 25 ′ UTR两个区域的构建体的5′ UTR中，表明TOP 2、RPA 1和DHFR-TSmRNA的5′ UTR中存在的八聚体共有序列是TOP 2 mRNA正常循环所必需的。在一个只含有一个共有八聚体的质粒构建体中，TOP25 ′ UTR的共有八聚体序列发生突变，并显示质粒编码的TOP2 mRNA的正常循环，导致mRNA水平的循环显著降低。这些结果表明，在细胞周期中，TOP 2 mRNA的负调控机制涉及在TOP 2 mRNA的5′ UTR内含有一个或多个保守八聚体序列的冗余元件。
Gene expression in trypanosomatids appears to be regulated largely at the posttranscriptional level and involves maturation of mRNA precursors bytranssplicing of a 39-nucleotide miniexon sequence to the 5′ end of the mRNA and cleavage and polyadenylation at the 3′ end of the mRNA. To initiate the identification of sequences involved in the periodic expression of DNA replication genes in trypanosomatids, we have mapped splice acceptor sites in the 5′ flanking region of theTOP2gene, which encodes the kinetoplast DNA topoisomerase, and have carried out deletion analysis of this region on a plasmid-encodedTOP2gene. Block deletions within the 5′ untranslated region (UTR) identified two regions (−608 to −388 and −387 to −186) responsible for periodic accumulation of the mRNA. Deletion of one or the other of these sequences had no effect on periodic expression of the mRNA, while deletion of both regions resulted in constitutive expression of the mRNA throughout the cell cycle. Subcloning of these sequences into the 5′ UTR of a construct lacking both regions of theTOP25′ UTR has shown that an octamer consensus sequence present in the 5′ UTR of theTOP2, RPA1,andDHFR-TSmRNAs is required for normal cycling of theTOP2mRNA. Mutation of the consensus octamer sequence in theTOP25′ UTR in a plasmid construct containing only a single consensus octamer and that shows normal cycling of the plasmid-encodedTOP2mRNA resulted in substantial reduction of the cycling of the mRNA level. These results imply a negative regulation ofTOP2mRNA during the cell cycle by a mechanism involving redundant elements containing one or more copies of a conserved octamer sequence within the 5′ UTR ofTOP2mRNA.