RESUMO
Hepatitis B virus (HBV) infection remains a major health problem worldwide. Maintenance of the covalently closed circular DNA (cccDNA), which serves as a template for HBV RNA transcription, is responsible for the failure of eradicating chronic HBV during current antiviral therapy. cccDNA is assembled with cellular histone proteins into chromatin, but little is known about the regulation of HBV chromatin by histone posttranslational modifications. In this study, we identified silent mating type information regulation 2 homolog 3 (SIRT3) as a host factor restricting HBV transcription and replication by screening seven members of the sirtuin family, which is the class III histone deacetylase. Ectopic SIRT3 expression significantly reduced total HBV RNAs, 3.5-kb RNA, as well as replicative intermediate DNA in HBV-infected HepG2-Na+ /taurocholate cotransporting polypeptide cells and primary human hepatocytes. In contrast, gene silencing of SIRT3 promoted HBV transcription and replication. A mechanistic study found that nuclear SIRT3 was recruited to the HBV cccDNA, where it deacetylated histone 3 lysine 9. Importantly, occupancy of SIRT3 on cccDNA could increase the recruitment of histone methyltransferase suppressor of variegation 3-9 homolog 1 to cccDNA and decrease recruitment of SET domain containing 1A, leading to a marked increase of trimethyl-histone H3 (Lys9) and a decrease of trimethyl-histone H3 (Lys4) on cccDNA. Moreover, SIRT3-mediated HBV cccDNA transcriptional repression involved decreased binding of host RNA polymerase II and transcription factor Yin Yang 1 to cccDNA. Finally, hepatitis B viral X protein could relieve SIRT3-mediated cccDNA transcriptional repression by inhibiting both SIRT3 expression and its recruitment to cccDNA. CONCLUSION: SIRT3 is a host factor epigenetically restricting HBV cccDNA transcription by acting cooperatively with histone methyltransferase; these data provide a rationale for the use of SIRT3 activators in the prevention or treatment of HBV infection. (Hepatology 2018).
Assuntos
DNA Viral/genética , Epigênese Genética/genética , Hepatite B/genética , Domínios PR-SET/genética , Sirtuína 3/genética , Replicação Viral/genética , DNA Complementar/genética , Hepatite B/fisiopatologia , Vírus da Hepatite B/genética , Histona Metiltransferases/metabolismo , Humanos , Reação em Cadeia da Polimerase em Tempo Real/métodos , Sensibilidade e EspecificidadeRESUMO
In order to remove low concentration of phosphorus in wastewater and realize resource utilization of reed, reed biochar(RB) was prepared using reed and then modified by ferric chloride, and the adsorption behavior of low concentration phosphorus was investigated. The results showed that the iron content of modified reed biochar(MRB) was 11.98 mg·g-1, which was 44.7 times that of RB; pHpzc of the MRB was 7.49, and the adsorption effect was the best when the solution pH was 7.0; at the initial concentration of 4.0 mg·L-1 and temperature of 298K, the adsorption capacity of MRB was 0.658 mg·g-1, which was 34.6 times that of RB. The adsorption isotherms at different temperatures were well fitted to Langmiur equation, which indicated the adsorption was monolayer adsorption, and increasing temperature was favorable for adsorption. ΔGθ<0, ΔHθ>0 and ΔSθ>0 indicated that the adsorption was a spontaneous, entropy increasing and endothermic process. The kinetic experimental data of the adsorption fitted well to the pseudo-second-order equation, the initial adsorption rate increased with the increasing initial concentration of solution, and the adsorption was mainly controlled by intraparticle diffusion. The research will provide basic data for application of MRB in deep removal of low concentration phosphorus from sewage treatment plant and water body.