Latent infections with periodic reactivation are a common outcome after acute infection with many viruses. The latency-associated transcript ( LAT ) gene is required for wild-type reactivation of herpes simplex virus (HSV). However, the underlying mechanisms remain unclear. In rabbit trigeminal ganglia, extensive apoptosis occurred with LAT − virus but not with LAT + viruses. In addition, a plasmid expressing LAT blocked apoptosis in cultured cells. Thus, LAT promotes neuronal survival after HSV-1 infection by reducing apoptosis.

Prostate cancer can be detected using assays for blood-borne prostate-specific antigen (PSA), which is the clinically most useful diagnostic marker of malignant disease. This paper characterizes the 5-flanking prostate-specific enhancer which controls expression of the human PSA gene This enhancer, located between ؊5824 and ؊3738, is androgen-responsive and requires a promoter for activity. Inductions of 12-100-fold activity occur at 1 nM concentrations of the testosterone analog R1881. The enhancer demonstrated tissue specificity as judged by transfections of several human cell lines. Electrophoretic mobility shift assays comparing nuclear extracts from breast cancer cells MCF-7, and prostate cancer cells LNCaP, showed three regions of prostatespecific binding. These three regions are ؊4168 to ؊4797 (region I), ؊4710 to 4479 (region II), and ؊4168 to ؊3801 (region III). Region III contained a putative androgen response element at ؊4136 that markedly affected activity if mutated. These data suggest that prostate-specific gene expression may involve interaction of prostatespecific proteins or protein complexes with the enhancer in addition to binding of the androgen receptor to androgen response elements.

The latency-associated transcript (LAT) is the only abundant herpes simplex virus type 1 (HSV-1) transcript expressed during latency. In the rabbit eye model, LAT null mutants do not reactivate efficiently from latency. We recently demonstrated that the LAT null mutant dLAT2903 induces increased levels of apoptosis in trigeminal ganglia of infected rabbits compared to LAT ؉ strains (G. We previously showed that a mutant expressing just the first 1.5 kb of LAT has wild-type spontaneous reactivation in rabbits, and a mutant expressing just the first 811 nucleotides of LAT has a reactivation frequency higher than that of dLAT2903 but lower than that of wild-type virus. In addition, mutants reported here for the first time, expressing just the first 661 or 76 nucleotides of LAT, had spontaneous reactivation indistinguishable from that of the LAT null mutant dLAT2903. In summary, these studies provide evidence that there is a functional relationship between the ability of LAT to promote cell survival and its ability to enhance spontaneous reactivation.-Following ocular, oral, or intranasal infection, herpes simplex virus type 1 (HSV-1) establishes latent infection in trigeminal ganglia (TG) (3, 4). The only abundant viral transcript expressed in latently infected neurons is the latency-associated transcript (LAT) (11,12,32,48,51,54). The primary 8.3-kb primary LAT transcript is unstable and is spliced, yielding an abundant stable 2-kb LAT (12,48,53,56) that is a stable intron (17, 33). LAT is antisense to ICP0 and is primarily localized in the nucleus. This has led to the suggestion that LAT represses ICP0 expression by an antisense mechanism (48), which in turn represses productive infection (8,20). However, we previously showed that the first 1.5 kb of the primary LAT is sufficient for spontaneous reactivation from latency (45). Since this region does not overlap ICP0, antisense repression of ICP0 expression by LAT is not required for spontaneous reactivation in the rabbit model. Although LAT is important for latency in smallanimal models (27,52), its functional roles during the latencyreactivation cycle are not understood.In transient-transfection assays, a LAT fragment (LAT nucleotides 301 to 2659) encompassing the stable 2-kb LAT derived from strain KOS enhanced cell survival following an apoptotic insult (42). The same study also demonstrated that a McKrae LAT Ϫ mutant (dLAT2903) had increased levels of apoptosis in rabbit TG. These findings suggested that LAT is important for latent infections because it promotes survival of infected neurons.HSV-1 can induce or inhibit apoptosis (programmed cell death) in a cell type-dependent manner after infection of cultured cells (1,2,18,19,36). Several antiapoptotic genes have been identified (1,2,18,42), suggesting that regulation of apoptosis is crucial for the virus's life cycle. Trauma, stress, or other imbalances of growth factors or cytokines can induce neuronal apoptosis, and neuronal apoptosis is linked to neurodegenerative disorders (7,21,23,26,35,(38)(39)(40). H...

The herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) is abundantly expressed in latently infected trigeminal ganglionic sensory neurons. Expression of the first 1.5 kb of LAT coding sequences is sufficient for the wild-type reactivation phenotype in small animal models of infection. The ability of the first 1.5 kb of LAT coding sequences to inhibit apoptosis is important for the latency-reactivation cycle. Several studies have also concluded that LAT inhibits productive infection. To date, a functional LAT protein has not been identified, suggesting that LAT is a regulatory RNA. Two small RNAs (sRNAs) were previously identified within the first 1.5 kb of LAT coding sequences. In this study, we demonstrated that both LAT sRNAs were expressed in the trigeminal ganglia of mice latently infected with an HSV-1 strain that expresses LAT but not when mice were infected with a LAT null mutant. LAT sRNA1 and sRNA2 cooperated to inhibit cold shockinduced apoptosis in mouse neuroblastoma cells. LAT sRNA1, but not LAT sRNA2, inhibited apoptosis less efficiently than both sRNAs. When rabbit skin cells were cotransfected with plasmids that express LAT sRNA1 and HSV-1 genomic DNA, the amount of infectious virus released was reduced approximately 3 logs. Although LAT sRNA2 was less effective at inhibiting virus production, it inhibited expression of infected cell protein 4 (ICP4). Neither LAT sRNA had an obvious effect on ICP0 expression. These studies suggested that expression of two LAT sRNAs plays a role in the latency-reactivation cycle by inhibiting apoptosis and productive infection.Most adults in the United States harbor latent herpes simplex virus type 1 (HSV-1) (48, 71) in sensory neurons located in trigeminal ganglia (TG) or sacral dorsal root ganglia (34, 68). Acute infection is typically initiated in the mucocutaneous epithelium. Despite a vigorous immune response during acute infection, HSV-1 establishes latency in sensory neurons. Latent HSV-1 periodically reactivates from latency, resulting in the shedding of infectious virus and various recurrent clinical disorders (reviewed in references 34 and 35).Mice, rabbits, or humans latently infected with HSV-1 express abundant levels of the latency-associated transcript (LAT) in latently infected neurons (12,14,15,38,45,62,65,69,70). The primary LAT transcript is 8.3 kb, and splicing yields a stable 2-kb LAT and an unstable 6.3-kb LAT (14,62,73). The 2-kb LAT can be further spliced in infected neurons (43). The majority of the 2-kb LAT is not capped or polyadenylated and appears to be a stable intron (19,40). In general, HSV-1 LAT null mutants do not reactivate from latency as efficiently as LAT-expressing strains (reviewed in references 34, 35, and 68). Expression of the first 1.5 kb of LAT coding sequences (LAT nucleotides [nt] 1 to 1499) is crucial for wildtype (wt) levels of reactivation in small animal models (28,33,56).LAT reduces apoptosis in infected tissue culture cells (32) and promotes neuronal survival in the TG of infected rabbits (53...