Nuclear export of human hepatitis B virus core protein and pregenomic RNA depends on the cellular NXF1-p15 machinery

• Published in: PloS one Vol. 9; no. 10; p. e106683
• Main Authors: Yang, Ching-Chun, Huang, Er-Yi, Li, Hung-Cheng, Su, Pei-Yi, Shih, Chiaho
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 31.10.2014; Public Library of Science (PLoS)
• Subjects: Accumulation; Active Transport, Cell Nucleus - genetics; Antigens; Arginine; Biology and Life Sciences; Cell culture; Cell Line; Cell Nucleus; Cloning; Core protein; Cytoplasm; Cytoplasm - genetics; Deoxyribonucleic acid; DNA; DNA Replication; Exports; Genomes; Hepatitis; Hepatitis B; Hepatitis B virus - genetics; Hepatitis B virus - metabolism; Host-Pathogen Interactions; Humans; Liver; Localization; Mammalian cells; mRNA processing; Multiprotein Complexes - genetics; Multiprotein Complexes - metabolism; Nuclear Export Signals; Nuclear transport; Nuclei; Nucleocytoplasmic Transport Proteins - genetics; Nucleocytoplasmic Transport Proteins - metabolism; Plasmids; Post-transcription; Protein Structure, Tertiary; Protein transport; Proteins; Reverse transcription; Ribonucleic acid; RNA; RNA transport; RNA Transport - genetics; RNA, Messenger - genetics; RNA, Small Interfering; RNA, Viral - metabolism; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; Rodents; siRNA; Spacecraft components; Viral Core Proteins - genetics; Viral Core Proteins - metabolism; Viruses; United States > US; Taiwan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0106683

Hepatitis B virus (HBV) core protein (HBc) can shuttle between nucleus and cytoplasm. Cytoplasm-predominant HBc is clinically associated with severe liver inflammation. Previously, we found that HBc arginine-rich domain (ARD) can associate with a host factor NXF1 (TAP) by coimmunoprecipitation. It is well known that NXF1-p15 heterodimer can serve as a major export receptor of nuclear mRNA as a ribonucleoprotein complex (RNP). In the NXF1-p15 pathway, TREX (transcription/export) complex plays an important role in coupling nuclear pre-mRNA processing with mRNA export in mammalian cells. Here, we tested the hypothesis whether HBc and HBV specific RNA can be exported via the TREX and NXF1-p15 mediated pathway. We demonstrated here that HBc can physically and specifically associate with TREX components, and the NXF1-p15 export receptor by coimmunoprecipitation. Accumulation of HBc protein in the nucleus can be induced by the interference with TREX and NXF1-p15 mediated RNA export machinery. HBV transcripts encodes a non-spliced 3.5 kb pregenomic RNA (pgRNA) which can serve as a template for reverse transcription. Cytoplasmic HBV pgRNA appeared to be reduced by siRNA treatment specific for the NXF1-p15 complex by quantitative RT-qPCR and Northern blot analyses. This result suggests that the pgRNA was also exported via the NXF1-p15 machinery. We entertain the hypothesis that HBc protein can be exported as an RNP cargo via the mRNA export pathway by hijacking the TREX and NXF1-p15 complex. In our current and previous studies, HBc is not required for pgRNA accumulation in the cytoplasm. Furthermore, HBc ARD can mediate nuclear export of a chimeric protein containing HBc ARD in a pgRNA-independent manner. Taken together, it suggests that while both pgRNA and HBc protein exports are dependent on NXF1-p15, they are using the same export machinery in a manner independent of each other.