Sequence Requirements for Interaction of Human Herpesvirus 7 Origin Binding Protein with the Origin of Lytic Replication

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Abstract
As do human herpesvirus 6 variants A and B (HHV-6A and -6B), HHV-7 encodes a homolog of the alphaherpesvirus origin binding protein (OBP), which binds at sites in the origin of lytic replication ( ori Lyt) to initiate DNA replication. In this study, we sought to characterize the interaction of the HHV-7 OBP (OBP H7 ) with its cognate sites in the 600-bp HHV-7 ori Lyt. We expressed the carboxyl-terminal domain of OBP H7 and found that amino acids 484 to 787 of OBP H7 were sufficient for DNA binding activity by electrophoretic mobility shift analysis. OBP H7 has one high-affinity binding site (OBP-2) located on one flank of an AT-rich spacer element and a low-affinity site (OBP-1) on the other. This is in contrast to the HHV-6B OBP (OBP H6B ), which binds with similar affinity to its two cognate OBP sites in the HHV-6B ori Lyt. The minimal recognition element of the OBP-2 site was mapped to a 14-bp sequence. The OBP H7 consensus recognition sequence of the 9-bp core, BRT YCWCC T (where B is a T, G, or C; R is a G or A; Y is a T or C; and W is a T or A), overlaps with the OBP H6B consensus YGW YCWCC Y and establishes YCWCC as the roseolovirus OBP core recognition sequence. Heteroduplex analysis suggests that OBP H7 interacts along one face of the DNA helix, with the major groove, as do OBP H6B and herpes simplex virus type 1 OBP. Together, these results illustrate both conserved and divergent DNA binding properties between OBP H7 and OBP H6B .