Poliovirus-associated protein kinase: destabilization of the virus capsid and stimulation of the phosphorylation reaction by Zn2+

Abstract

The previously described poliovirus-associated protein kinase activity phosphorylates viral proteins VPO and VP2 as well as exogenous proteins in the presence of Mg2+. In this paper, the effect of Zn2+ on the phosphorylation reaction and the stability of the poliovirus capsid has been studied in detail and compared to that of Mg2+. Phosphorylation patterns of viral and other proteins depend on the divalent cation present. In the presence of Zn2+, phosphorylation of capsid proteins VP2 and VP4 is significantly higher while phosphorylation of VPO and exogenous phosphate acceptor proteins is not detected. Our results indicate the activation of more than one virus-associated protein kinase by Zn2+. The ion-dependent behavior of the enzyme activities is observed independently of whether the virus was obtained from HeLa or green monkey kidney cells. The poliovirus capsid is destabilized by Zn2+. The destabilization leads to a substantially increased permeability of virus particles to ethidium bromide and RNase, concomitant with decreased infectivity of the sample. This alteration of the poliovirus capsid structure is a prerequisite for effective phosphorylation of viral capsid proteins. The increased level of phosphorylation of viral capsid proteins results in further destabilization of the viral capsid. As a result of the conformational changes, poliovirus-associated protein kinase activities dissociate from the virus particle. High-performance liquid chromatography-purified viral protein VP2 is phosphorylated by the released enzymes on serine, threonine, and tyrosine in the presence of Zn2+. We suggest that the destabilizing effect of phosphorylation on the viral capsid plays a role in uncoating of poliovirus.

The Capsid Protein of a Plant Single-stranded RNA Virus Is Modified by O-Linked N-Acetylglucosamine

“…An effect of protein phosphorylation on the stability of poliovirus capsids and its consequent involvement in viral uncoating was described some years ago (31). More recently, it has been shown that phosphorylation of PVA CP affects its capacity to interact with RNA, suggesting that this modification might contribute to the control of the amount of genomic RNA available for translation, replication, encapsidation, and movement (16).…”

Differential activities of the human immunodeficiency virus type 1-encoded Vpu protein are regulated by phosphorylation and occur in different cellular compartments

“…the regulation of cellular processes, it is not surprising that virus-encoded proteins have adopted this mode of regulation as well. For example, a poliovirus-associated protein kinase has been implicated in the phosphorylation-dependent destabilization of the viral capsid during the uncoating process (30).…”

Phosphorylation of Human Papillomavirus Type 16 L2 Contributes to Efficient Virus Infectious Entry

“…These results offer interesting parallels with a number of other viruses such as poliovirus, human immunodeficiency virus type 1 (HIV-1), hepatitis B virus, and human respiratory syncytial virus (HRSV) for which the phosphorylation of the viral capsid proteins has been shown to affect infectious entry and capsid stability and disassembly (50)(51)(52)(53). In the case of PVs, it would appear that phosphorylation at a site just downstream of the transmembrane domain of L2 aids capsid disassembly.…”