The HBV Core Protein and Core Particle Both Bind to the PPiase Par14 and Par17 to Enhance Their Stabilities and HBV Replication

• Published in: Frontiers in microbiology Vol. 12; p. 795047
• Main Authors: Saeed, Umar, Piracha, Zahra Zahid, Kwon, Hyeonjoong, Kim, Jumi, Kalsoom, Fadia, Chwae, Yong-Joon, Park, Sun, Shin, Ho-Joon, Lee, Hyun Woong, Lim, Jin Hong, Kim, Kyongmin
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 14.12.2021
• Subjects: HBV replication study; Hepatitis B virus; Microbiology; parvulin 14; parvulin 17; PPIase activity; parvulin 17; PPIase activity; Hepatitis B virus; parvulin 14; HBV replication study
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2021.795047

We recently reported that the PPIase Par14 and Par17 encoded by upregulate HBV replication in an HBx-dependent manner by binding to conserved arginine-proline (RP) motifs of HBx. HBV core protein (HBc) has a conserved RP motif; therefore, we investigated whether Par14/Par17 bind to HBc and/or core particles. Native agarose gel electrophoresis (NAGE) and immunoblotting and co-immunoprecipitation were used. Chromatin immunoprecipitation from HBV-infected HepG2-hNTCP-C9 cells was performed. NAGE and immunoblotting revealed that Par14/Par17 bound to core particles and co-immunoprecipitation revealed that Par14/Par17 interacted with core particle assembly-defective, and dimer-positive HBc-Y132A. Thus, core particles and HBc interact with Par14/Par17. Par14/Par17 interacted with the HBc RP motif possibly substrate-binding E46/D74 and E71/D99 motifs. Although Par14/Par17 dissociated from core particles upon heat treatment, they were detected in 0.2 N NaOH-treated opened-up core particles, demonstrating that Par14/Par17 bind outside and inside core particles. Furthermore, these interactions enhanced the stabilities of HBc and core particles. Like HBc-Y132A, HBc-R133D and HBc-R133E were core particle assembly-defective and dimer-positive, demonstrating that a negatively charged residue at position 133 cannot be tolerated for particle assembly. Although positively charged R133 is solely important for Par14/17 interactions, the RP motif is important for efficient HBV replication. Chromatin immunoprecipitation from HBV-infected cells revealed that the S19 and E46/D74 residues of Par14 and S44 and E71/D99 residues of Par17 were involved in recruitment of RP motif-containing HBc into cccDNA. Our results demonstrate that interactions of HBc, Par14/Par17, and cccDNA in the nucleus and core particle-Par14/Par17 interactions in the cytoplasm are important for HBV replication.