Harrison G P, Miele G, Hunter E, Lever A M
Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
J Virol. 1998 Jul;72(7):5886-96. doi: 10.1128/JVI.72.7.5886-5896.1998.
Packaging of type C retrovirus genomic RNAs into budding virions requires a highly specific interaction between the viral Gag precursor and unique cis-acting packaging signals on the full-length RNA genome, allowing the selection of this RNA species from among a pool of spliced viral RNAs and similar cellular RNAs. This process is thought to involve RNA secondary and tertiary structural motifs since there is little conservation of the primary sequence of this region between retroviruses. To confirm RNA secondary structures, which we and others have predicted for this region, disruptive, compensatory, and deletion mutations were introduced into proviral constructs, which were then assayed in a permissive cell line. Disruption of either of two predicted stem-loops was found to greatly reduce RNA encapsidation and replication, whereas compensatory mutations restoring base pairing to these stem-loops had a wild-type phenotype. A GGNGR motif was identified in the loops of three hairpins in this region. Results were consistent with the hypothesis that the process of efficient RNA encapsidation is linked to dimerization. Replication and encapsidation were shown to occur at a reduced rate in the absence of the previously described kissing hairpin motif.
C型逆转录病毒基因组RNA包装到出芽的病毒粒子中，需要病毒Gag前体与全长RNA基因组上独特的顺式作用包装信号之间进行高度特异性的相互作用，从而能够从剪接的病毒RNA和类似的细胞RNA池中选择这种RNA种类。由于逆转录病毒之间该区域的一级序列几乎没有保守性，因此该过程被认为涉及RNA二级和三级结构基序。为了证实我们和其他人预测的该区域的RNA二级结构，将破坏性、补偿性和缺失性突变引入原病毒构建体，然后在允许的细胞系中进行检测。发现破坏两个预测的茎环中的任何一个都会大大降低RNA的包装和复制，而恢复这些茎环碱基配对的补偿性突变具有野生型表型。在该区域的三个发夹环中鉴定出一个GGNGR基序。结果与有效RNA包装过程与二聚化相关的假设一致。在没有先前描述的亲吻发夹基序的情况下，复制和包装显示以降低的速率发生。
