The Binding Site of Transcription Factor YY1 Is Required for Intramolecular Recombination between Terminally Repeated Sequences of Linear Replicative Hepatitis B Virus DNA

In the replication cycle of hepadnavirus DNA, the double-stranded linear form of viral DNA is generated as a minor replicative intermediate, which is efficiently converted to covalently closed circular DNA (cccDNA) by intramolecular recombination (W. Yang and J. Summers, J. Virol. 69:4029–4036, 1995). We previously found a binding site of transcription factor Yin and Yang 1 (YY1) in one terminal region of the double-stranded linear replicative hepatitis B virus (HBV) DNA (M. Nakanishi-Matsui, Y. Hayashi, Y. Kitamura, and K. Koike, J. Virol. 74:5562–5568, 2000). However, it is not known whether the YY1-binding site is required for the intramolecular recombination of HBV DNA. In this study, we established an HBV-producing system in which the cccDNA appeared to be generated from the transfected linear DNA or the linear replicative DNA by nonhomologous end joining (NHEJ) or by both NHEJ and homologous recombination between terminally repeated sequences, respectively. When the YY1-binding site in the terminal region of transfected linear viral DNA was mutated, the cccDNA was generated merely by NHEJ. Results suggest that the YY1-binding site in the terminal region of linear replicative HBV DNA is required for intramolecular recombination between terminally repeated sequences.