UL52 Primase Interactions in the HSV-1 Helicase-Primase are Affected by Antiviral Compounds and Mutations Causing Drug Resistance. [Microbiology]
October 2nd, 2014 by Muylaert, I., Zhao, Z., Elias, P.
Herpes simplex virus 1, HSV-1, UL5/8/52 helicase-primase complex is required for DNA unwinding at the replication fork and synthesis of primers during virus replication, and it has become a promising novel target for antiviral therapy. Using molecular cloning we have identified three separate domains of UL52. Co-immunoprecipitation experiments in extracts from cells transiently expressing HA-tagged UL5, FLAG-UL8 and eGFP-tagged UL52 domains revealed that the amino-terminal domain of UL52 primase binds UL5 helicase and the middle domain interacts with the UL8 accessory protein. In addition, an interaction between the single-strand DNA binding protein ICP8 and the UL52 middle domain was observed. The complex between UL5 and UL52 is stabilized by the antiviral compound BAY 54-6322 and mutations providing resistance to the drug obliterate this effect. Our results also suggests a mechanism for accommodating conformational strain resulting from movement of UL5 and UL52 in opposite directions on the lagging strand template, and they identify molecular complexes which can be further examined by structural biology techniques to resolve the mechanism of primer synthesis during herpesvirus replication. Finally, they help to explain the mechanism of action of a novel class of antiviral compounds currently evaluated in clinical trials.