Herpes Simplex Virus Defective Genomes: Structure of HSV-1 ANG Defective DNA of Class II and Encoded Polypeptides

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Abstract
Sequence organization and origin of herpes simplex virus type 1 strain Angelotti (ANG) class II defective DNA (HSV-1 ANG dDNAl) were examined in detail by establishing physical maps and by molecular cloning. dDNAl consists of concatemers of tandem repeat units in which sequences from the UL region spanning map coordinates 0.37-0.415 of standard HSV ANG DNA are covalently linked to TRs/IRs sequences. The size of the repeat unit was .apprx. 8.9 kilobase pairs (kb), comprising sequences of 7.3 kb from UL and 1.6 kb from TRs/IRs regions. UL sequences were delineated by restriction enzyme sites KpnI N-P and EcoRI F-M, and were colinear with the corresponding sequences of the standard (wild-type) virus genome. Expression of dDNAl was studied in African green monkey kidney cells and in Xenopus laevis oocytes. A major polypeptide of MW .apprx. 135,000 (135K) was overproduced, suggesting that this protein was encoded by dDNAl. By several parameters (e.g., size, immune cross-reactivity and affinity for native and denatured DNA), the 135K polypeptide was identified as the major HSV DNA-binding protein. The repeat unit contains part of the DNA polymerase gene as demonstrated by its ability to rescue some mutations in this gene.