Identification of serotonin 2A receptor as a novel HCV entry factor by a chemical biology strategy

Hepatitis C virus (HCV) is a leading cause of liver disease worldwide. Although several HCV protease/polymerase inhibitors were recently approved by U.S. FDA, the combination of antivirals targeting multiple processes of HCV lifecycle would optimize anti-HCV therapy and against potential drug-resistance. Viral entry is an essential target step for antiviral development, but FDA-approved HCV entry inhibitor remains exclusive. Here we identify serotonin 2A receptor (5-HTR) is a HCV entry factor amendable to therapeutic intervention by a chemical biology strategy. The silencing of 5-HTR and clinically available 5-HTR antagonist suppress cell culture-derived HCV (HCVcc) in different liver cells and primary human hepatocytes at late endocytosis process. The mechanism is related to regulate the correct plasma membrane localization of claudin 1 (CLDN1). Moreover, phenoxybenzamine (PBZ), an FDA-approved 5-HTR antagonist, inhibits all major HCV genotypes in vitro and displays synergy in combination with clinical used anti-HCV drugs. The impact of PBZ on HCV genotype 2a is documented in immune-competent humanized transgenic mice. Our results not only expand the understanding of HCV entry, but also present a promising target for the invention of HCV entry inhibitor.

RNA binding protein 24 regulates the translation and replication of hepatitis C virus

The secondary structures of hepatitis C virus (HCV) RNA and the cellular proteins that bind to them are important for modulating both translation and RNA replication. However, the sets of RNA-binding proteins involved in the regulation of HCV translation, replication and encapsidation remain unknown. Here, we identified RNA binding motif protein 24 (RBM24) as a host factor participated in HCV translation and replication. Knockdown of RBM24 reduced HCV propagation in Huh7.5.1 cells. An enhanced translation and delayed RNA synthesis during the early phase of infection was observed in RBM24 silencing cells. However, both overexpression of RBM24 and recombinant human RBM24 protein suppressed HCV IRES-mediated translation. Further analysis revealed that the assembly of the 80S ribosome on the HCV IRES was interrupted by RBM24 protein through binding to the 5'-UTR. RBM24 could also interact with HCV Core and enhance the interaction of Core and 5'-UTR, which suppresses the expression of HCV. Moreover, RBM24 enhanced the interaction between the 5'- and 3'-UTRs in the HCV genome, which probably explained its requirement in HCV genome replication. Therefore, RBM24 is a novel host factor involved in HCV replication and may function at the switch from translation to replication.

In vitro study of type Ⅰ intron-mediated dual reporter gene imaging for carcinoembryonic antigen / 中华核医学与分子影像杂志

Objective To develop a specific trans-splicing intron ribozyme type Ⅰ-mediated dual reporter gene system (Rib53-Fluc-tk) for targeting CEA.Methods The novel CEA-targeting trans-splicing ribozyme with the downstream reporter system (Rib53-Fluc-tk) was constructed by genetic engineering technology.The trans-splicing reaction product was evaluated using the 131I-5-iodo-2'-fluro-l-beta-D-arabinofuranosy-luracil (FIAU) cellular uptake rates and the bioluminescence.Two-sample t test,the analysis of variance and the least significant difference (LSD) t test was performed for data analysis.Results The sequence of Rib53-Fluc-tk was proved by gene-sequencing test.Human MCF-7 breast cancer cells showed a high ratio of firefly luciferase/renilla luciferase (0.64±0.10,n =4).A 520 bp band of product existed,which matched with the predicted size using RNA from cells transfected with Rib53-Fluc-tk in MCF-7.Signals were detected by bioluminescence in human embryonic kidney 293T cells co-transfected with Rib53-Fluc-tk and pCDNA3.1-CEA.The labelling rate of 131I-FIAU was (64.02±4.79)％ (n =3).The radiochemical purity was (95.96± 1.07)％ (n=3),and the stability of the radiocompound remained high in human serum at least for 24 h.The uptake of 131I-FIAU in 293T cells transfected with Rib53-Fluc-tk was (0.31±0.01)％ (n=4),while it increased with the incubation time in 293T cells co-transfected with pCDNA3.1-CEA and Rib53-Fluc-tk and reached (1.40±0.06)％ at 4.5 h (F=1 007.29,t=136.34,both P＜0.01).Conelusions A novel and specific reporter gene in the cellular level was established.Taking advantage of trans-splicing reaction of the ribozyme,it could improve the specificity of the reporter gene imaging.