Transcriptional regulation of precore and pregenomic RNAs of hepatitis B virus

Abstract

Hepatitis B virus (HBV) infection, either acute or chronic, has been one of the leading health problems in the world. To understand the HBV life cycle and disease process, we set out to study the regulation of viral gene expression. In this paper, we report the characterization of the HBV core promoter: two 3.5-kb transcripts, precore and pregenomic, are made from it. The latter is itself a template for viral genome replication and also encodes viral proteins essential for both viral replication and virion assembly. We identify a short sequence (from nucleotides [nt] 1744 to 1851, referred to as the basic core promoter [BCP]) that is sufficient to direct correct initiation of both precore and pregenomic messages. In addition, the two appear to be regulated in a coordinate manner. Sequences upstream of the BCP (from nt 1636 to 1744, referred to as the core upstream regulatory sequence [CURS]), have a strong stimulating effect on the BCP. Addition of the CURS to the BCP leads to a dramatic increase in both the transcription of two 3.5-kb messages and the production of 42-nm virions from transiently transfected hepatoma cells. The CURS stimulates the BCP in a position- and orientation-dependent manner. Therefore, it is unlikely that the effect is mediated through enhancer II, which has been localized to the same sequence. Deletion analysis of the CURS suggests that it contains multiple regulatory elements that control the BCP in an interactive manner. In accord with this hypothesis, the CURS is found to be bound with many distinct protein factors in footprinting experiments. Among these elements, box alpha (from nt 1646 to 1668) and box gamma delta (from nt 1671 to 1703) are two regulatory elements which individually stimulate promoter activity more than 100-fold.

High Prevalence of 1762T 1764A Mutations in the Basic Core Promoter of Hepatitis B Virus Isolated From Black Africans With Hepatocellular Carcinoma Compared With Asymptomatic Carriers

“…First, it contains the BCP and part of enhancer II, which are important in the control of transcription of both precore mRNA and pgRNA. 35 Precore mRNA is translated into the precore-core fusion protein that is post-translationally modified into soluble HBeAg, whereas pgRNA is translated into core and polymerase proteins and is reverse transcribed into minus-strand DNA. Second, this region encodes the carboxylterminus of the X protein, which has transactivating functions.…”

Hepatitis B Virus with X Gene Mutation Is Associated with the Majority of Serologically “Silent” Non‐B, Non‐C Chronic Hepatitis

“…The X region is reported to be necessary for the production of infectious progeny virus in susceptible hosts from experiments in vivo using X gene mutants of woodchuck hepatitis virus (WHV) (4,39). The X region contains many important elements for HBV proliferation including the core promoter (38), a negative regulatory element that abolishes the function of the core promoter (11) and enhancer II (36,37). DR1 and DR2, which are implicated in the origin of HBV DNA, are also located in the X region (25).…”

Suppression of p38 mitogen-activated protein kinase inhibits hepatitis B virus replication in human hepatoma cell: the antiviral role of nitric oxide

“…Plasmids and reagents pHBV3.6 that consists of more than unit lengths of the HBV genome that include sequence from 1636 to 1990 [14] was kindly provided by Dr L.-P. Ting (Department of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan). pEGFP-N1 containing the EGFP gene was purchased from BD Biosciences Clontech (Palo Alto, CA, USA).…”

“…To investigate the involvement of MAPKs in HBV replication, we first used pHBV3.6, a plasmid consisting of more than unit lengths of the HBV genome that includes sequence from 1636 to 1990 [14], to transfect the human hepatoma cell line, Huh7, and determined MAPK activation by Western blot. At 14 or 24 h post-transfection, p38 MAPK phosphorylation could be enhanced in the pHBV3.6-transfected cells, but not in the control plasmid, or pEGFP-N1-transfected cells.…”