Chemical modification of nucleotide bases and mRNA editing depend on hexamer or nucleoprotein phase in Sendai virus nucleocapsids
Chemical modification of nucleotide bases and mRNA editing depend on hexamer or nucleoprotein phase in Sendai virus nucleocapsids
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DOI：
10.1017/s1355838202029977
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发表时间：
2002-08-01
期刊：
影响因子：
4.5
通讯作者：
Kolakofsky, D
中科院分区：
文献类型：
--
作者：
Iseni, F;Baudin, F;Kolakofsky, D
仙台病毒的负链基因组是核衣壳蛋白（N）和RNA的组装体，其中每个N亚基精确地与6个核苷酸相关。只有长度为6 nt的倍数的基因组才能有效复制或天然存在，并且它们的复制启动子含有具有六聚体重复的序列元件。受这种六聚体规则支配的副粘病毒也在其合成期间通过G插入，经由病毒RNA聚合酶的受控形式“口吃”（假模板转录）编辑其P基因mRNA。这种口吃是由顺式作用序列（3' UNN UUUUU CCC）指导的，其六聚体相在每个病毒组中是保守的。为了确定核衣壳内给定核苷酸序列的六聚体相位是否影响其对化学修饰的敏感性，以及mRNA编辑位点的六聚体相位是否对编辑过程很重要，我们制备了一组匹配的病毒，其中模型编辑位点相对于基因组末端每次置换1个核苷酸。检查了这些仙台病毒在细胞培养感染中编辑其mRNA的相对能力，并研究了DMS化学修饰静息病毒核衣壳内顺式作用信号的核苷酸的能力。在六聚体阶段1和6的胞苷是最容易化学修饰，而mRNA编辑是最广泛的口吃时，网站C的位置2至5。显然，N亚基印记了与其相关的核苷酸序列，并影响病毒RNA合成和mRNA编辑的起始。因此，N-亚基组合似乎在遗传密码上插入了另一个密码。
The minus-strand genome of Sendai virus is an assembly of the nucleocapsid protein (N) and RNA, in which each N subunit is associated with precisely 6 nt. Only genomes that are a multiple of 6 nt long replicate efficiently or are found naturally, and their replication promoters contain sequence elements with hexamer repeats. Paramyxoviruses that are governed by this hexamer rule also edit their P gene mRNA during its synthesis, by G insertions, via a controlled form of viral RNA polymerase "stuttering" (pseudo-templated transcription). This stuttering is directed by a cis-acting sequence (3' UNN UUUUUU CCC), whose hexamer phase is conserved within each virus group. To determine whether the hexamer phase of a given nucleotide sequence within nucleocapsids affected its sensitivity to chemical modification, and whether hexamer phase of the mRNA editing site was important for the editing process, we prepared a matched set of viruses in which a model editing site was displaced 1 nt at a time relative to the genome ends. The relative abilities of these Sendai viruses to edit their mRNAs in cell culture infections were examined, and the ability of DMS to chemically modify the nucleotides of this cis-acting signal within resting viral nucleocapsids was also studied. Cytidines at hexamer phases 1 and 6 were the most accessible to chemical modification, whereas mRNA editing was most extensive when the stutter-site C was in positions 2 to 5. Apparently, the N subunit imprints the nucleotide sequence it is associated with, and affects both the initiation of viral RNA synthesis and mRNA editing. The N-subunit assembly thus appears to superimpose another code upon the genetic code.