Abstract
Hepatitis delta virus (HDV) RNA forms an unbranched rod-like structure and complexes with the delta antigen (HDAg). Host ADAR1-catalyzed RNA editing at the amber/W site of the small HDAg leads to the production of the large HDAg, which inhibits replication and is required for virion assembly. For HDV genotype 1, amber/W editing is controlled by HDAg and the RNA structure immediate vicinity and downstream of the editing site. Here, the effects of 20 mutants carrying an increased length of consecutive base-pairing at various sites in HDV RNA on amber/W site editing were examined. All nine mutants carrying genomic regions that formed up to 15 consecutive base pairs, which is also the maximum length observed in 41 naturally occurring HDV genomes, showed normal editing rate. However, mutants carrying a 16 or 17 consecutive base-paired antigenomic segment located as far as 114 nt upstream could increase editing efficiency, possibly by interfering with HDAg binding. These data show for the first time that extended base-pairing upstream of the amber/W site could increase HDV RNA editing efficiency. Furthermore, it appears that the naturally occurring HDV RNA structures have been selected for suboptimal amber/W RNA editing, which favors the HDV replication cycle.
Highlights
Hepatitis delta virus (HDV) virion is composed of hepatitis B virus surface antigens (HBsAgs) surrounding a ribonucleoprotein (RNP) complex that comprises the circular RNA genome and multiple copies of the delta antigen (HDAg) [1,2,3]
The unbranched rod-like RNA structure, comprising short base-paired segments interspersed with small bulges, plays important roles in the HDV replication cycle [4,20]
For HDV-1, this amber/W site occurs as an A-C mismatch pair in the midst of 8 bp, and that increased base-pairing in the region 15 to 25 nt downstream, but not upstream, of the HDV amber/W editing site significantly increases editing [9]
Summary
Hepatitis delta virus (HDV) virion is composed of hepatitis B virus surface antigens (HBsAgs) surrounding a ribonucleoprotein (RNP) complex that comprises the circular RNA genome and multiple copies of the delta antigen (HDAg) [1,2,3]. The latter is the sole HDV-encoded protein and occurs as small and large forms. The HDV genome and its replication intermediate, the antigenome, both form a characteristic unbranched rod-like structure, in which. The isolates can differ in sequence by as much as 40%, the unbranched rod-like structure of the HDV
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