Short, duplicated sequence indicative of the recombinogenicity of the junction between a unique and an inverted repeat sequence in the S component of the herpes simplex virus type 1 genome.

A herpes simplex virus type 1 (HSV-1) strain, B3, was found to have a short duplication on the left junction between the unique sequence (US) and the inverted repeat sequence (RS) in the S component of the genome DNA. A short region of RS contiguous to the left US-RS junction was duplicated in B3. Based on the nucleotide sequences in and around the US-RS junctions of B3 and other HSV-1 strains, a concept of junction stretch was proposed. The organization of junction stretch is RS side 5'-(G or A stretch)AGC-3' US side. Introduction of the concept of junction stretch led to a definition of the structure in and around the US-RS junction, in the form common to HSV-1 strains. The right end of US in the HSV-1 genome was the A of the ATG initiation codon of gene US12, and thus the ATG triplet may act as a buffer to prevent expansion of RS, as is the case with HSV-2. The duplication in B3 was generated by a crossover event between a point on RS and the US side end of the left junction stretch. These observations suggest that the US side end of the junction stretch possesses the property of recombinogenicity, responsible for generation of the duplication in strain B3 and also for the formation of the US-RS junction of HSV.