Sequence of the Putative Origin of Replication in the UL Region of Herpes Simplex Virus Type 1 ANG DNA

Abstract

Interest has been stimulated concerning the region mapping between 0.38 and 0.42 on the prototype configuration of the herpes simplex virus type 1 (HSV-1) genome due to the high probability of the presence there of a second origin of DNA replication. A 960 bp restriction fragment (HinfI E) of a class II defective HSV-1 ANG DNA has been sequenced using the viral DNA rather than molecularly cloned DNA. This fragment includes the BamHI U/R cleavage site, mapping at approximately 0.4. Part of the sequence derived in this study displays homology with the origins of DNA replication contained in TR_S/IR_S of HSV-1 and HSV-2 DNA. The homologous region comprising 76 bp occurs as two copies, each of which contains two palindromically arranged copies of an 8 bp sequence identical to the ‘consensus’ sequence reported to be part of the origin of DNA replication at the terminus of the mammalian adenoviruses. It can be deduced from a comparison of this structure to the TR_S/IR_S origin of HSV-1 and HSV-2 that there are two origins of replication in the U_L region of HSV-1 ANG DNA. Assuming that the orientation of the consensus sequence is relevant to the direction of DNA replication, one can conclude that the U_L origin(s) of HSV-1 ANG is (are) bidirectional. It has not yet been possible to clone DNA fragments molecularly which include the region spanning the U_L origin(s) of HSV-1 DNA.