The cleavage products from coronavirus polyproteins, known as the non-structural proteins (nsps), are believed to make up the major components of the viral replication/transcription complex. In this study, several nsps encoded by avian gammacoronavirus infectious bronchitis virus (IBV) were screened for RNA-binding activity and interaction with its RNA-dependent RNA polymerase, nsp12. Nsp2, nsp5, nsp8, nsp9 and nsp10 were found to bind to untranslated regions (UTRs), while nsp8 was confirmed to interact with nsp12. Nsp8 has been reported to interact with nsp7 and functions as a primase synthesizing RNA primers for nsp12. Further characterization revealed that nsp8-nsp12 interaction is independent of the UTRs of viral RNA, and nsp8 interacts with both the N- and C-terminal regions of nsp12. These results have prompted a proposal of how the nsp7-nsp8 complex could possibly function in tandem with nsp12, forming a highly efficient complex that could synthesize both the RNA primer and viral RNA during coronavirus infection.

冠状病毒多蛋白的裂解产物，称为非结构蛋白（nsps），据信构成病毒复制/转录复合物的主要成分。在这项研究中，筛选了由禽伽马冠状病毒感染性支气管炎病毒（IBV）编码的几种nsps的RNA结合活性及其与RNA依赖的RNA聚合酶nsp12的相互作用。发现Nsp2，nsp5，nsp8，nsp9和nsp10结合到非翻译区（UTR），而nsp8被证实与nsp12相互作用。据报道，Nsp8与nsp7相互作用，并用作合成nsp12的引物酶合成RNA引物。进一步的特征表明，nsp8-nsp12相互作用与病毒RNA的UTR无关，并且nsp8与nsp12的N和C端区域都相互作用。