In:
Journal of Virology, American Society for Microbiology, Vol. 78, No. 20 ( 2004-10-15), p. 10856-10864
Abstract:
The X gene of hepatitis B virus (HBV) is one of the major factors in HBV-induced hepatocarcinogenesis and is essential for the establishment of productive HBV replication in vivo. Recent studies have shown that the X gene product targets mitochondria and induces calcium flux, thereby activating Ca + -dependent signal transduction pathways. However, regulatory mechanisms of X gene expression have remained unclear. Previous studies had localized a minimal promoter activity to a 21-bp GC-rich sequence located 130 bp upstream of the X protein coding region and showed that there was a cellular protein bound to this DNA. Interestingly, the 21-bp sequence identified as an X gene minimal promoter does not contain any previously identified core promoter elements, such as a TATA box. To better understand the mechanisms of transcriptional initiation of the X gene, we set out to biochemically purify the binding protein(s) for the 21-bp DNA. We report here the identification of the X gene minimal promoter-binding activity as nuclear respiratory factor 1 (NRF1), a previously known transcription factor that activates the majority of nucleus-encoded mitochondrial genes and various housekeeping genes. Primer extension analyses of the X mRNAs show that mutations at the binding site specifically inactivate transcription from this promoter and that a dominant-negative NRF1 mutant and short interfering RNAs inhibit transcription from this promoter. Therefore, NRF1 specifically binds the 21-bp minimal promoter and positively contributes to transcription of the X gene. Simultaneous activation of the X gene and mitochondrial genes by NRF1 may allow the X protein to target mitochondria most efficiently.
Type of Medium:
Online Resource
ISSN:
0022-538X
,
1098-5514
DOI:
10.1128/JVI.78.20.10856-10864.2004
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2004
detail.hit.zdb_id:
1495529-5
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