Involvement of Host ATR-CHK1 Pathway in Hepatitis B Virus Covalently Closed Circular DNA Formation

ABSTRACT The covalently closed circular (CCC) DNA of hepatitis B virus (HBV) functions as the only viral transcriptional template capable of producing all viral RNA species and is essential to initiate and sustain viral replication. CCC DNA is converted from a relaxed circular (RC) DNA, in which nei...

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Autores principales:	Jun Luo, Laurie Luckenbaugh, Hui Hu, Zhipeng Yan, Lu Gao, Jianming Hu
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	ATR CCC DNA CHK1 DNA damage checkpoint DNA damage repair cccDNA Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/342fda5c28d14647b4492bc2800ff555
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spelling	oai:doaj.org-article:342fda5c28d14647b4492bc2800ff5552021-11-15T15:56:58ZInvolvement of Host ATR-CHK1 Pathway in Hepatitis B Virus Covalently Closed Circular DNA Formation10.1128/mBio.03423-192150-7511https://doaj.org/article/342fda5c28d14647b4492bc2800ff5552020-02-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.03423-19https://doaj.org/toc/2150-7511ABSTRACT The covalently closed circular (CCC) DNA of hepatitis B virus (HBV) functions as the only viral transcriptional template capable of producing all viral RNA species and is essential to initiate and sustain viral replication. CCC DNA is converted from a relaxed circular (RC) DNA, in which neither of the two DNA strands is covalently closed. As RC DNA mimics damaged cellular DNA, the host cell DNA damage repair (DDR) system is thought to be responsible for HBV CCC DNA formation. The potential role of two major cellular DDR pathways, the ataxia telangiectasia mutated (ATM) pathway and the ATM and Rad3-related (ATR) pathway, in HBV CCC DNA formation was thus investigated. Inhibition, or expression knockdown, of ATR and its downstream signaling factor CHK1, but not of ATM, decreased CCC DNA formation during de novo HBV infection, as well as intracellular CCC DNA amplification, when RC DNA from extracellular virions and intracellular nucleocapsids, respectively, is converted to CCC DNA. Furthermore, a novel RC DNA processing product with 5′ truncated minus strands was detected when the ATR-CHK1 pathway was inhibited, further indicating that this pathway controls RC DNA processing during its conversion to CCC DNA. These results provide new insights into how host cells recognize and process HBV RC DNA in order to produce CCC DNA and have implications for potential means to block CCC DNA production. IMPORTANCE Hepatitis B virus (HBV) chronically infects hundreds of millions of people and remains a major cause of viral hepatitis, cirrhosis, and liver cancer. HBV persistence is sustained by a viral nuclear episome that directs all viral gene expression needed to support viral replication. The episome is converted from an incomplete DNA precursor in viral particles in an ill-understood process. We report here that the incomplete DNA precursor is recognized by the host cell in a way similar to the sensing of damaged cellular DNA for subsequent repair to form the nuclear episome. Intense efforts are ongoing to develop novel antiviral strategies to eliminate CCC DNA so as to cure chronic HBV infection. Our results here provide novel insights into, and suggest novel ways of perturbing, the process of episome formation. Furthermore, our results inform mechanisms of cellular DNA damage recognition and repair, processes essential for normal cell growth.Jun LuoLaurie LuckenbaughHui HuZhipeng YanLu GaoJianming HuAmerican Society for MicrobiologyarticleATRCCC DNACHK1DNA damage checkpointDNA damage repaircccDNAMicrobiologyQR1-502ENmBio, Vol 11, Iss 1 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	ATR CCC DNA CHK1 DNA damage checkpoint DNA damage repair cccDNA Microbiology QR1-502
spellingShingle	ATR CCC DNA CHK1 DNA damage checkpoint DNA damage repair cccDNA Microbiology QR1-502 Jun Luo Laurie Luckenbaugh Hui Hu Zhipeng Yan Lu Gao Jianming Hu Involvement of Host ATR-CHK1 Pathway in Hepatitis B Virus Covalently Closed Circular DNA Formation
description	ABSTRACT The covalently closed circular (CCC) DNA of hepatitis B virus (HBV) functions as the only viral transcriptional template capable of producing all viral RNA species and is essential to initiate and sustain viral replication. CCC DNA is converted from a relaxed circular (RC) DNA, in which neither of the two DNA strands is covalently closed. As RC DNA mimics damaged cellular DNA, the host cell DNA damage repair (DDR) system is thought to be responsible for HBV CCC DNA formation. The potential role of two major cellular DDR pathways, the ataxia telangiectasia mutated (ATM) pathway and the ATM and Rad3-related (ATR) pathway, in HBV CCC DNA formation was thus investigated. Inhibition, or expression knockdown, of ATR and its downstream signaling factor CHK1, but not of ATM, decreased CCC DNA formation during de novo HBV infection, as well as intracellular CCC DNA amplification, when RC DNA from extracellular virions and intracellular nucleocapsids, respectively, is converted to CCC DNA. Furthermore, a novel RC DNA processing product with 5′ truncated minus strands was detected when the ATR-CHK1 pathway was inhibited, further indicating that this pathway controls RC DNA processing during its conversion to CCC DNA. These results provide new insights into how host cells recognize and process HBV RC DNA in order to produce CCC DNA and have implications for potential means to block CCC DNA production. IMPORTANCE Hepatitis B virus (HBV) chronically infects hundreds of millions of people and remains a major cause of viral hepatitis, cirrhosis, and liver cancer. HBV persistence is sustained by a viral nuclear episome that directs all viral gene expression needed to support viral replication. The episome is converted from an incomplete DNA precursor in viral particles in an ill-understood process. We report here that the incomplete DNA precursor is recognized by the host cell in a way similar to the sensing of damaged cellular DNA for subsequent repair to form the nuclear episome. Intense efforts are ongoing to develop novel antiviral strategies to eliminate CCC DNA so as to cure chronic HBV infection. Our results here provide novel insights into, and suggest novel ways of perturbing, the process of episome formation. Furthermore, our results inform mechanisms of cellular DNA damage recognition and repair, processes essential for normal cell growth.
format	article
author	Jun Luo Laurie Luckenbaugh Hui Hu Zhipeng Yan Lu Gao Jianming Hu
author_facet	Jun Luo Laurie Luckenbaugh Hui Hu Zhipeng Yan Lu Gao Jianming Hu
author_sort	Jun Luo
title	Involvement of Host ATR-CHK1 Pathway in Hepatitis B Virus Covalently Closed Circular DNA Formation
title_short	Involvement of Host ATR-CHK1 Pathway in Hepatitis B Virus Covalently Closed Circular DNA Formation
title_full	Involvement of Host ATR-CHK1 Pathway in Hepatitis B Virus Covalently Closed Circular DNA Formation
title_fullStr	Involvement of Host ATR-CHK1 Pathway in Hepatitis B Virus Covalently Closed Circular DNA Formation
title_full_unstemmed	Involvement of Host ATR-CHK1 Pathway in Hepatitis B Virus Covalently Closed Circular DNA Formation
title_sort	involvement of host atr-chk1 pathway in hepatitis b virus covalently closed circular dna formation
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/342fda5c28d14647b4492bc2800ff555
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Involvement of Host ATR-CHK1 Pathway in Hepatitis B Virus Covalently Closed Circular DNA Formation

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