Sekiba Kazuma, Miyake Nozomi, Miyakawa Yu, Shibata Chikako, Seimiya Takahiro, Kishikawa Takahiro, Fujishiro Mitsuhiro, Otsuka Motoyuki
Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
Department of Gastroenterology and Hepatology, Academic Field of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Hepatol Commun. 2025 Jul 14;9(8). doi: 10.1097/HC9.0000000000000757. eCollection 2025 Aug 1.
The long-term goal of chronic hepatitis B research is a functional cure (HBsAg seroclearance). Although currently used nucleos(t)ide analogs can efficiently inhibit viral replication, they do not reduce viral RNAs or proteins produced from covalently closed circular DNA (cccDNA), and rarely achieve a functional cure. To overcome this situation, revealing the mode of the existence of cccDNA is required, including identifying the interreacting proteins with cccDNA. Here, we aimed to identify novel proteins that interact with cccDNA.
Using an in vitro HBV infection model and a sequence-specific proximity labelling method consisting of dead Cas9 and biotin identification (BioID2), we comprehensively determined proteins that possibly interact with cccDNA. After identifying the candidate proteins, the HBV RNA transcription levels were examined by knocking out the associated genes.
We identified ABHD14B as a protein that interacts with cccDNA and inhibits HBV RNA transcription from cccDNA. ABHD14B decreases the acetylation levels of histone proteins that control the transcription levels of HBV RNA in cccDNA. Moreover, ABHD14B interacts with TFII-I, which binds directly to cccDNA in a sequence-dependent manner. These results suggest that the host protein, ABHD14B, is recruited to cccDNA via the TFII-I protein, inhibiting HBV RNA transcription from cccDNA by deacetylating cccDNA histones.
ABHD14B was newly identified as a suppressor of HBV RNA transcription from cccDNA, which may improve our understanding of the mode of existence of cccDNA, providing a basis for development of a functional cure.
慢性乙型肝炎研究的长期目标是实现功能性治愈（乙肝表面抗原血清学清除）。尽管目前使用的核苷（酸）类似物能够有效抑制病毒复制，但它们并不能减少共价闭合环状DNA（cccDNA）产生的病毒RNA或蛋白质，很少能实现功能性治愈。为克服这种情况，需要揭示cccDNA的存在模式，包括鉴定与cccDNA相互作用的蛋白质。在此，我们旨在鉴定与cccDNA相互作用的新蛋白质。
利用体外乙肝病毒感染模型和由失活的Cas9与生物素识别（BioID2）组成的序列特异性邻近标记方法，我们全面确定了可能与cccDNA相互作用的蛋白质。在鉴定出候选蛋白质后，通过敲除相关基因检测乙肝病毒RNA转录水平。
我们鉴定出ABHD14B是一种与cccDNA相互作用并抑制cccDNA转录乙肝病毒RNA的蛋白质。ABHD14B降低了控制cccDNA中乙肝病毒RNA转录水平的组蛋白的乙酰化水平。此外，ABHD14B与TFII-I相互作用，TFII-I以序列依赖的方式直接结合到cccDNA上。这些结果表明，宿主蛋白ABHD14B通过TFII-I蛋白被招募到cccDNA，通过使cccDNA组蛋白去乙酰化来抑制cccDNA转录乙肝病毒RNA。
ABHD14B被新鉴定为cccDNA转录乙肝病毒RNA的抑制剂，这可能增进我们对cccDNA存在模式的理解，为开发功能性治愈方法提供依据。
