title: Characterization of human herpesvirus 6A/B U94 as ATPase, helicase, exonuclease and DNA-binding proteins.
abstract: Human herpesvirus-6A (HHV-6A) and HHV-6B integrate their genomes into the telomeres of human chromosomes, however, the mechanisms leading to integration remain unknown. HHV-6A/B encode a protein that has been proposed to be involved in integration termed U94, an ortholog of adeno-associated virus type 2 (AAV-2) Rep68 integrase. In this report, we addressed whether purified recombinant maltose-binding protein (MBP)-U94 fusion proteins of HHV-6A/B possess biological functions compatible with viral integration. We could demonstrate that MBP-U94 efficiently binds both dsDNA and ssDNA containing telomeric repeats using gel shift assay and surface plasmon resonance. MBP-U94 is also able to hydrolyze adenosine triphosphate (ATP) to ADP, providing the energy for further catalytic activities. In addition, U94 displays a 3' to 5' exonuclease activity on dsDNA with a preference for 3'-recessed ends. Once the DNA strand reaches 8-10 nt in length, the enzyme dissociates it from the complementary strand. Lastly, MBP-U94 compromises the integrity of a synthetic telomeric D-loop through exonuclease attack at the 3' end of the invading strand. The preferential DNA binding of MBP-U94 to telomeric sequences, its ability to hydrolyze ATP and its exonuclease/helicase activities suggest that U94 possesses all functions required for HHV-6A/B chromosomal integration.
authors.affiliation: Division of Infectious Disease and Immunity, CHU de Québec Research Center, Quebec city, Quebec G1V 4G2, Canada.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Trempe
authors.affiliation: Division of Infectious Disease and Immunity, CHU de Québec Research Center, Quebec city, Quebec G1V 4G2, Canada.
authors.forename: Annie
authors.initials: A
authors.lastname: Gravel
authors.affiliation: Division of Infectious Disease and Immunity, CHU de Québec Research Center, Quebec city, Quebec G1V 4G2, Canada.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Dubuc
authors.affiliation: Institut für Virologie, Freie Universität Berlin, Berlin 14163, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Wallaschek
authors.affiliation: Division of Infectious Disease and Immunity, CHU de Québec Research Center, Quebec city, Quebec G1V 4G2, Canada.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Collin
authors.affiliation: Division of Infectious Disease and Immunity, CHU de Québec Research Center, Quebec city, Quebec G1V 4G2, Canada.
authors.forename: Shella
authors.initials: S
authors.lastname: Gilbert-Girard
authors.affiliation: Division of Infectious Disease and Immunity, CHU de Québec Research Center, Quebec city, Quebec G1V 4G2, Canada.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Morissette
authors.affiliation: Institut für Virologie, Freie Universität Berlin, Berlin 14163, Germany.
authors.forename: Benedikt B
authors.initials: BB
authors.lastname: Kaufer
authors.affiliation: Division of Infectious Disease and Immunity, CHU de Québec Research Center, Quebec city, Quebec G1V 4G2, Canada Department of microbiology, infectious disease and immunology, Faculty of Medicine, Université Laval, Quebec city, Québec,G1V 0A6 Canada Louis.flamand@crchul.ulaval.ca.
authors.forename: Louis
authors.initials: L
authors.lastname: Flamand
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D004265:DNA Helicases / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000737:chemistry / Q000378:metabolism*; D015654:Herpesvirus 6, Human / Q000201:enzymology*; D011485:Protein Binding; D016415:Sequence Alignment; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D014764:Viral Proteins; C068734:rep proteins, Adeno-associated virus 2; D005090:Exodeoxyribonucleases; D000251:Adenosine Triphosphatases; D004265:DNA Helicases