The spontaneous reactivation function of the herpes simplex virus type 1 LAT gene resides completely within the first 1.5 kilobases of the 8.3-kilobase primary transcript

Abstract

The herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) gene is essential for efficient spontaneous reactivation of HSV-1 from latency. We report here that although the LAT gene is 8.3 kb in length, the first 1.5 kb of the LAT gene alone is sufficient for wild-type levels of spontaneous reactivation. We began with a LAT deletion mutant of HSV-1 strain McKrae in which the LAT promoter and the first 1.6 kb of the 5 end of the LAT gene had been deleted from both copies of LAT (one in each viral long repeat). As we previously reported, this mutant (dLAT2903) was significantly impaired for spontaneous reactivation (G. C. Perng, E. C.

Herpes simplex virus 1 regulates β-catenin expression in TG neurons during the latency-reactivation cycle

“…LAT is the only viral gene product abundantly expressed in latently infected neurons and thus was an important comparison to wt LAT +/+ HSV-1 [34]. The dLAT2903 mutant virus used for this study contains a deletion from -161 to +1667 relative to the start of the primary 8.3-kb LAT: consequently, dLAT2903 does not express detectable levels of LAT, and reactivation from latency in rabbits and mice is significantly reduced [34][35][36][37]. The LAT -/mutant (dLAT2903) was marker repaired back to wt (dLAT2903R) and has identical properties as the parental wt McKrae strain of HSV-1 [34, 35]: therefore, dLAT2903R is referred to as wt HSV-1 throughout this study.…”

A Herpes Simplex Virus Type 1 Latency-Associated Transcript Mutant with Increased Virulence and Reduced Spontaneous Reactivation

“…The parental McKrae virus and all mutants were triple plaque purified and passaged only one or two times prior to use. The construction and properties of dLAT2903, LAT3.3A (previously designated LAT1.5a), and dLAT371 have been previously described (14,17,18).…”

“…LAT's function also does not appear to be due to antisense downregulation of the important immediate-early gene ICP0, which LAT overlaps in an antisense direction. We recently showed that the first 1.5 kb of LAT alone is sufficient for wild-type levels of spontaneous reactivation (17). This region does not overlap any portion of any known HSV-1 gene.…”

“…This primary LAT transcript gives rise to a family of LAT RNAs, including the very stable 2-kb LAT (20,24,25), which appears to be an intron produced by splicing (6). LAT transcription-negative mutants have been shown to reactivate poorly by explant or induced reactivation in the mouse (9,10,21), by induced reactivation in the rabbit (1,23), and by spontaneous reactivation in the rabbit (14,17). Thus, LAT is essential for efficient, wild-type reactivation from sensory neurons.…”

“…This region does not overlap any portion of any known HSV-1 gene. Mapping a LAT spontaneous reactivation function to the first 1.5 kb of LAT was done by inserting the LAT promoter and the first 1.5 kb of LAT into an ectopic location in the genome of a LAT null mutant between HSV-1 genes UL37 and UL38 (17). This completely restored wild-type levels of spontaneous reactivation.…”