Expression and function of structural proteins of paramyxovirus transcription complex

人副流感病毒2型（human parainfluenza virus type 2，hPIV 2）是副粘病毒的一种，其V基因转录成V和P两种mRNA，V mRNA是V基因的忠实转录物，而P mRNA在hPIV 2感染的哺乳动物细胞中通过RNA编辑机制转录。因此，P和V蛋白都在细胞中翻译。我们构建了重组杆状病毒含有原始的V基因，其中有7个G残基在其编辑位点和一个操纵的V基因，其中有10个G残基在其编辑位点。出乎意料的是，当V基因在重组杆状病毒感染的昆虫细胞中表达时，除了V蛋白外，还合成了少量的P蛋白。此外，当在昆虫细胞中表达含有V基因的重组杆状病毒时，P蛋白的合成增加，所述V基因在其编辑位点具有延长的G残基atretch长度，即10个G残基。P和V蛋白都是在体外翻译重组杆状病毒感染细胞的mRNA中合成的。此外，在mRNA中检测到G-残基插入和缺失，而在体外翻译的V RNA中未检测到P蛋白，该V RNA由T7 RNA聚合酶体外转录。这些结果表明，非模板化的G残基插入和删除在转录水平上没有副粘病毒L蛋白。

V gene of human parainfluenza virus type 2 (hPIV2) , a member of paramyxoviruses, is transcribed into both a V and a P mRNA.The V mRNA is a faithful transcript of the V gene, however the P mRNA is transcribed by RNA editing mechanism in hPIV2-infected mammalian cells. Thus both the P and the V proteins are translated in the cells. We constructed recombinant baculoviruses containing the original V gene, which has seven G residues at its editing site and a manipulated V gene, which has ten G residues at its editing site. Unexpectedly, a small amount of the P protein was synthesized in addition to the V protein when the V gene was expressed in the recombinant baculovirus-infected insect cells. Furthermore, synthesis of the P protein increased when a recombinant baculovirus containing a V gene, which has extended length of G residue atretch, that is ten G residues, at its editing site, was expressed in the insect cells. Both the P and the V proteins were synthesized in in vitro translation of mRNA from the recombinant baculovirus-infected cells. Moreover, both G-residue insertions and a deletion were detected in mRNA.While the P protein was not detected in in vitro translation of the V RNA that was transcribed in vitro by T7 RNA polymerase. These results suggest that the non-templated G residues were inserted and deleted at the transcription level without paramyxovirus L protein.