The herpes simplex virus latency-associated transcript is spliced during the latent phase of infection.

The herpes simplex virus type 1 latency-associated transcript (LAT) is expressed as a major species 2,100 to 2,200 bases in length and a less abundant one ca. 730 bases shorter in latently infected mouse and rabbit neurons. RNA blot hybridization experiments using 20- to 22-base synthetic oligonucleotides and mung bean nuclease protection assays have demonstrated that the smaller LAT species is colinear with the larger one, except for a 730-base intron. On the basis of Northern blot analysis, the spliced species which comprises as much as 50% of the total LAT in latent infections of mice with several strains of herpes simplex virus type 1 and latent infections of rabbits with either the McKrae or the KOS(M) strains of virus is not present in the acute phase of infection. Further and rather surprisingly, in mice latently infected with the KOS(M) strain of virus, the spliced LAT species is considerably less abundant. This suggests that both the strain of virus and the animal in which the latent infection occurs are important in either the processing or stability of spliced LAT. Finally, an exhaustive series of experiments failed to provide convincing evidence that a unique, poly(A)+ species of LAT exists in the latent phase of infection.