Biology subjects

Taketomi, A.

Publications and source records attributed to Taketomi, A..

3 recordsLinked to original sources

bioRxiv2024

Involvement of Hepatitis B Core-Related Antigen in Viral Genome Integration in Patients With Prior Hepatitis B Virus Infection

BackgroundThe incidence of non-B non-C hepatocellular carcinoma (NBNC-HCC), which is negative for hepatitis B surface antigen and hepatitis C virus antibodies, is on the rise. Relatively high numbers of NBNC-HCC patients are hepatitis B core antibody (HBcAb) positive, suggesting that previous HBV infection may play a role in NBNC-HCC development, though the exact mechanisms are unclear. This study aimed to investigate whether HBV genomes are integrated into the host genome of HBcAb-positive NBNC-HCC cases and how these integrations may contribute to cancer development and progression. MethodsHBV detection PCR using HBV-specific primers on DNA extracted from HBcAb-positive NBNC-HCC tissue samples was performed. Positive samples were further examined for HBV integration sites using viral DNA-capture sequencing. Additionally, hepatitis B core-related antigen (HBcrAg) serum levels were measured to assess whether they could be predictive for HBV detection PCR results. ResultsAmong 90 HBcAb-positive NBNC-HCC samples, HBV genome amplification was detected in 18 samples, and elevated HBcrAg levels were associated with the HBV detection PCR results. Seventeen of these samples exhibited HBV integration. The HBV genome was integrated near the TERT gene in 7 samples, resulting in significantly increased TERT mRNA levels; in the KMT2B gene (2 samples); and downstream of LOC441666 (2 samples). ConclusionThe integration sites we identified in our samples have been previously reported in HBV-related HCC, suggesting that HBV integration may also contribute to hepatocarcinogenesis in HBcAb-positive NBNC-HCC. Furthermore, HBcrAg could serve as a potential, noninvasive marker for detecting HBV integration in these cases.

microbiology↗

bioRxiv2023

NEDD4-binding protein 1 suppresses HBV replication by degrading pgRNA

Chronic infection with hepatitis B virus (HBV) places patients at increased risk for liver cirrhosis and hepatocellular carcinoma. Although nucleos(t)ide analogs are mainly used for the treatment of HBV, they require long-term administration and may lead to the emergence of drug resistant mutants. Therefore, to identify targets for the development of novel anti-HBV drugs, we screened for HBV-suppressive host factors using a plasmid expression library of RNA-binding proteins (RBPs). We screened 132 RBPs using an expression plasmid library by measuring HBV relaxed circular DNA (rcDNA) levels in hepatocellular carcinoma. Our screen identified NEDD4-binding protein 1 (N4BP1) as having an anti-HBV effect. In hepatocellular carcinoma cell lines transfected or infected with HBV, overexpression of N4BP1 decreased rcDNA levels while knockdown or knockout of the gene encoding N4BP1 rescued rcDNA levels. N4BP1 possesses the KH-like and RNase domains and both were required for the anti-HBV effect of N4BP1. Additionally, we measured levels of HBV pregenomic RNA (pgRNA) and covalently closed circular DNA (cccDNA) in the RBP-transfected cells and confirmed that N4BP1 binds pgRNA directly and degraded both the 3.5 kb and 2.4/2.1 kb HBV RNA. In summary, N4BP1 is a newly identified host factor able to counteract HBV production by promoting the degradation of 3.5 kb and 2.1/2.4 kb HBV RNA. ImportanceThere is still a large number of HBV-infected people in the world today because of no curative treatment for HBV infection. In this study, we focused on and screened RNA-binding proteins to identify new host factors which inhibit HBV replication. As a result, we found that NEDD4-binding protein 1 (N4BP1) expression suppresses rcDNA production by promoting the degradation of pregenomic RNA, 2.4kb and 2.1kb HBV RNA. Furthermore, KH-like domain or RNase domain of N4BP1 were involved in this anti-HBV effect. In addition, the N4BP1 levels were lower in HCC resection samples of exacerbated patients, suggesting that individual N4BP1 levels might be related to HCC progression. This novel factor can potentially become a key to new HBV treatments.

microbiology↗

bioRxiv2018

USP15 participates in HCV propagation through the regulation of viral RNA translation and lipid droplet formation

Hepatitis C virus (HCV) utilizes cellular factors for an efficient propagation. Ubiquitin is covalently conjugated to the substrate to alter its stability or to modulate signal transduction. In this study, we examined the importance of ubiquitination for HCV propagation. We found that inhibition of de-ubiquitinating enzymes (DUBs) or overexpression of non-specific DUBs impaired HCV replication, suggesting that ubiquitination regulates HCV replication. To identify specific DUBs involved in HCV propagation, we set up an RNAi screening against DUBs and successfully identified ubiquitin-specific protease 15 (USP15) as a novel host factor for HCV propagation. Our studies showed that USP15 is involved in translation of HCV RNA and production of infectious HCV particles. In addition, deficiency of USP15 in human hepatic cell lines (Huh7 and Hep3B/miR122 cells) but not in a non-hepatic cell line (293T cells) impaired HCV propagation, suggesting that USP15 participates in HCV propagation through the regulation of hepatocyte-specific functions. Moreover, we showed that loss of USP15 had no effect on innate immune responses in vitro and in vivo. We also found that USP15-deficient Huh7 cells showed reductions in the sizes and numbers of lipid droplets (LDs), and addition of palmitic acids restored the production of infectious HCV particles. Taken together, these data suggest that USP15 participates in HCV propagation by regulating the translation of HCV RNA and formation of LDs.

microbiology↗