增加 HIV-1 基因组 RNA 中的 CpG 二核苷酸丰度可抑制病毒复制。
Increasing the CpG dinucleotide abundance in the HIV-1 genomic RNA inhibits viral replication.
机构信息
Department of Infectious Diseases, King's College London, 3rd Floor Borough Wing, Guy's Hospital, London, SE1 9RT, UK.
出版信息
Retrovirology. 2017 Nov 9;14(1):49. doi: 10.1186/s12977-017-0374-1.
BACKGROUND
The human immunodeficiency virus type 1 (HIV-1) structural protein Gag is necessary and sufficient to form viral particles. In addition to encoding the amino acid sequence for Gag, the underlying RNA sequence could encode cis-acting elements or nucleotide biases that are necessary for viral replication. Furthermore, RNA sequences that inhibit viral replication could be suppressed in gag. However, the functional relevance of RNA elements and nucleotide biases that promote or repress HIV-1 replication remain poorly understood.
RESULTS
To characterize if the RNA sequence in gag controls HIV-1 replication, the matrix (MA) region was codon modified, allowing the RNA sequence to be altered without affecting the protein sequence. Codon modification of nucleotides (nt) 22-261 or 22-378 in gag inhibited viral replication by decreasing genomic RNA (gRNA) abundance, gRNA stability, Gag expression, virion production and infectivity. Comparing the effect of these point mutations to deletions of the same region revealed that the mutations inhibited infectious virus production while the deletions did not. This demonstrated that codon modification introduced inhibitory sequences. There is a much lower than expected frequency of CpG dinucleotides in HIV-1 and codon modification introduced a substantial increase in CpG abundance. To determine if they are necessary for inhibition of HIV-1 replication, codons introducing CpG dinucleotides were mutated back to the wild type codon, which restored efficient Gag expression and infectious virion production. To determine if they are sufficient to inhibit viral replication, CpG dinucleotides were inserted into gag in the absence of other changes. The increased CpG dinucleotide content decreased HIV-1 infectivity and viral replication.
CONCLUSIONS
The HIV-1 RNA sequence contains low abundance of CpG dinucleotides. Increasing the abundance of CpG dinucleotides inhibits multiple steps of the viral life cycle, providing a functional explanation for why CpG dinucleotides are suppressed in HIV-1.
背景
人类免疫缺陷病毒 1 型（HIV-1）结构蛋白 Gag 是形成病毒颗粒所必需且充分的。除了编码 Gag 的氨基酸序列外，基础 RNA 序列还可以编码顺式作用元件或核苷酸偏倚，这些对于病毒复制是必要的。此外，可能会抑制 gag 中的抑制病毒复制的 RNA 序列。然而，促进或抑制 HIV-1 复制的 RNA 元件和核苷酸偏倚的功能相关性仍知之甚少。
结果
为了确定 gag 中的 RNA 序列是否控制 HIV-1 复制，对基质（MA）区进行了密码子修饰，使得 RNA 序列可以改变而不影响蛋白质序列。 gag 中核苷酸（nt）22-261 或 22-378 的密码子修饰通过减少基因组 RNA（gRNA）丰度、gRNA 稳定性、Gag 表达、病毒粒子产生和感染力来抑制病毒复制。将这些点突变的影响与相同区域的缺失进行比较表明，突变抑制了感染性病毒的产生，而缺失则没有。这表明密码子修饰引入了抑制性序列。HIV-1 中的 CpG 二核苷酸的频率远低于预期，密码子修饰大大增加了 CpG 的丰度。为了确定它们是否抑制 HIV-1 复制所必需，将引入 CpG 二核苷酸的密码子突变为野生型密码子，这恢复了有效的 Gag 表达和感染性病毒粒子的产生。为了确定它们是否足以抑制病毒复制，在没有其他变化的情况下将 CpG 二核苷酸插入 gag 中。增加 CpG 二核苷酸的含量降低了 HIV-1 的感染力和病毒复制。
结论
HIV-1 RNA 序列含有低丰度的 CpG 二核苷酸。增加 CpG 二核苷酸的丰度抑制了病毒生命周期的多个步骤，为 CpG 二核苷酸在 HIV-1 中被抑制提供了功能解释。
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