Previous work showed that conservation of proline
at residue 306 (rtP306) of hepatitis B virus
(HBV) reverse transcriptase (RT) is crucial for
virus replication and encapsidation of pregenomic
RNA (pgRNA). In this study, the functions
of residues flanking rtP306 in HBV RT (rtG304,
rtY305, rtA307, rtL308 and rtL311) are presented.
Alanine or phenylalanine was used to substitute
these residues by constructing site-directed
mutants which were used to transfect Huh-7
cells. Replication competencies and encapsidation
efficiencies were compared between the
mutants and the parental viral strain. Substitutions
at these residues resulted in marked
decrease of replication competency, which was
confirmed by Southern blot hybridization of HBV
DNA isolated from intracytoplasmic core particles,
and trans-complementation between a nonreplicative
defective mutant and corresponding
RT mutants. Impaired pgRNA encapsidation
efficiency of these mutants was shown as the
major mechanism for decreased replication efficiency.
Since residues from rt304 to rt311 are
highly conserved among genotypes A–H HBV
strains, results suggest that rt304 to rt311 in HBV
RT may serve as a putative anti-HBV new target
domain. J. Med. Virol. 79:676–682, 2007.