Amplification of a short nucleotide sequence in the repeat units of defective herpes simplex virus type 1 Angelotti DNA

Abstract

The reiterated regions TRS and IRS bracketing the US segment of herpes simplex virus type 1 Angelotti DNA are heterogeneous in size by stepwide insertion of 1-6 copies of a 550-base-pair nucleotide sequence. Considerably higher amplification of this sequence was observed in defective viral DNA: up to 14 copies were inserted in the repeat units of a major class of defective herpes simplex virus type 1 Angelotti DNA, dDNA1, which originated from noncontiguous sites located in UL and the inverted repeats of the S component of the parental genome. Physical maps were established for the cleavage sites of KpnI, PstI, XhoI and BamHI restriction endonucleases on the repeats of dDNA1. The map position of the insertion sequence was determined. The amplified inserts were not distributed at random among or within the repeats. A given total population of dDNA1 molecules consisted of different homopolymers, each of which contained a constant number of inserts in all of its repeats. Assuming that a rolling-circle mechanism is involved in the generation of full-length defective herpes simplex virus type 1 Angelotti DNA from single repeat units, the 550-base pair sequence is probably amplified in the repeats before the replication process.