In the course of latency, the genomes of above mentioned viruses survive in the form of non-integrated circularized double strand (ds) DNA molecules . For diagnostic purposes the presence of this DNA can be detected by polymerase chain reaction (PCR). The above mentioned latency state of viral DNA undergoes complex regulation. A set of non-coding transcripts called LAT (i.e. latency associated transcripts) interferes with early transcription. The LAT which are abundant in neurons, are also required for reactivation. In addition, they may promote neuronal survival, but may also induce apoptosis. Another regulatory RNA molecules antisense to the 5´end of LAT, were identified in the extracts from neuron-like cells and designated AL-RNA (anti-LAT sense RNA). The AL-RNA overlap the core LAT promoter at the first 158 nucleotides of the 5´-end of primary transcript; possibly they are related to the virulence of given HSV strain.
