马铃薯A病毒复制和CP调控需要CK2，CPIP和HSP70以及CHIP来调控。 - 中国病毒学论坛|我们一直在坚持！

We demonstrate here that coat protein (CP) phosphorylation by protein kinase CK2 and a chaperone system formed by two heat-shock proteins, CP-interacting protein (CPIP) and HSP70, are both essential for Potato virus A (PVA; genus Potyvirus) replication and that all of these host proteins have the capacity to contribute to the level of PVA CP accumulation. An E3 ubiquitin ligase called carboxyl terminus Hsc70-interacting protein (CHIP), which may participate in the CPIP-HSP70-mediated CP degradation, is also needed for robust PVA gene expression. Thr243 residue within the CK2 consensus sequence of PVA CP was found to be essential for viral replication and to regulate CP protein stability. Substitution of Thr243 either with a phosphorylation mimicking Asp (CPADA) or phosphorylation-deficient Ala (CPAAA) residue in CP expressed from viral RNA limited PVA gene expression to the level of non-replicating PVA. We found that both the CPAAA mutant and CK2 silencing inhibited, whereas CPADA mutant and overexpression of CK2 increased PVA translation. From our previous studies we know that phosphorylation reduces the RNA binding capacity of PVA CP and an excess of CP fully blocks viral RNA translation. Together, this suggest that binding by non-phosphorylated PVA CP represses viral RNA translation, involving further CP phosphorylation and CPIP-HSP70 chaperon activities as prerequisites for PVA replication. We propose that this mechanism contributes to shifting potyvirus RNA from translation to replication.

IMPORTANCE Host protein kinase CK2, two host chaperones CPIP and HSP70 and viral coat protein (CP) phosphorylation at Thr243 are needed for Potato virus A (PVA) replication. Our results show that non-phosphorylated CP blocks viral translation, likely via binding to viral RNA. We propose that this translational block is needed to allow time and space for the formation of potyviral replication complex around the 3’ end of viral RNA. Progression into replication involves CP regulation by both CK2 phosphorylation and chaperones CPIP and HSP70.