Structural basis for an essential subunit interaction in influenza virus RNA polymerase PB1-PB2

流感病毒RNA依赖性RNA聚合酶是一种多功能的异源三聚体，它通过“夺帽”机制产生病毒mRNA。宿主细胞mRNA被切割以产生带帽寡核苷酸，其可以使用病毒基因组RNA作为模板延伸。帽结合和核酸内切酶活性仅在病毒基因组RNA结合后被激活。这需要从RNA结合PB1亚基到帽结合PB2亚基的信号传导，并且这两个亚基之间的界面对于聚合酶活性是必不可少的。我们已经定义了这种相互作用的蛋白质晶体学表面，并测试了突变的接触残基上的全酶的功能的影响。这种新的界面是令人惊讶的小，但它在调节250 kDa聚合酶中起着至关重要的作用，并且在禽流感和人流感中完全保守。

Influenza virus RNA-dependent RNA polymerase is a multi-functional heterotrimer, which uses a "cap-snatching" mechanism to produce viral mRNA. Host cell mRNA is cleaved to yield a cap-bearing oligonucleotide which can be extended using viral genomic RNA as a template. The cap binding and endonuclease activities are only activated once viral genomic RNA is bound. This requires signaling from the RNA-binding PB1 subunit to the cap-binding PB2 subunit, and the interface between these two subunits is essential for polymerase activity. We have defined this interaction surface by protein crystallography, and tested the effects of mutating contact residues on the function of the holo-enzyme. This novel interface is surprisingly small, yet it plays a crucial role in regulating the 250 kDa polymerase, and is completely conserved among avian and human influenza.