An acutely and latently expressed herpes simplex virus 2 viral microRNA inhibits expression of ICP34.5, a viral neurovirulence factor

Abstract

Latency-associated transcript (LAT) sequences regulate herpes simplex virus (HSV) latency and reactivation from sensory neurons. We found a HSV-2 LAT-related microRNA (miRNA) designated miR-I in transfected and infected cells in vitro and in acutely and latently infected ganglia of guinea pigs in vivo. miR-I is also expressed in human sacral dorsal root ganglia latently infected with HSV-2. miR-I is expressed under the LAT promoter in vivo in infected sensory ganglia. We also predicted and identified a HSV-1 LAT exon-2 viral miRNA in a location similar to miR-I, implying a conserved mechanism in these closely related viruses. In transfected and infected cells, miR-I reduces expression of ICP34.5, a key viral neurovirulence factor. We hypothesize that miR-I may modulate the outcome of viral infection in the peripheral nervous system by functioning as a molecular switch for ICP34.5 expression.HSV ͉ latency-associated transcript ͉ latency ͉ reactivation ͉ human H erpes simplex virus 1 and 2 (HSV-1 and HSV-2) are closely related human herpes viruses. HSV-1 and HSV-2 establish lifelong incurable latency in and reactivate preferentially from trigeminal ganglia and dorsal root ganglia to cause oro-facial and genital herpes, respectively. Although infections are usually mild, these viruses can cause severe disease including encephalitis and neonatal herpes, and HSV-2 infection is a risk factor for HIV acquisition. The only readily detectable viral transcript during latency of both HSV-1 and HSV-2 is the noncoding latency-associated transcript (LAT), which is transcribed from within the long repeats of the viral genome ( Fig. 1) (1). A Ϸ8-kb primary LAT is spliced, yielding a stable Ϸ2-kb LAT intron (2). Deletion of the LAT promoter in both HSV-1 and HSV-2 reduces the efficiency of reactivation (3-5), and substitution of HSV-1 LAT for native HSV-2 LAT sequences confers an HSV-1 reactivation phenotype (6). The HSV-1 LAT is currently believed to act in part by increasing the establishment or maintenance of latency, likely via an effect on the survival of acutely infected neurons (7), which may be mediated by inhibition of apoptosis in infected neurons (8). The molecular function of HSV-2 LAT remains largely unknown.miRNAs are a family of 21Ϸ24-nt noncoding RNAs that regulate gene expression based on sequence similarity to their targets. Mammalian viruses including EBV, Kaposi's sarcoma-associated herpesvirus, human cytomegalovirus, and SV40 encode viral miRNAs (9). Viral encoded miRNAs were predicted for HSV-1 (10, 11) and also for HSV-2 (10). However, no miRNAs have been identified in HSV-2 or HSV-1 LAT sequences. Results HSV-2 LAT Exon 2 Encodes a miRNA.To find miRNAs within the HSV-2 LAT region, a plasmid containing the LAT sequence and its promoter (pSSK) and a mutant plasmid expressing LAT under control of the CMV-IE promoter (pCMV-SSK) were transfected into 293 cells. Small RNAs isolated from the transfected cells were cloned and sequenced. A 22-23-nt HSV-2 RNA sequence (designated HSV-2 miR-I) appeared at a frequenc...

Latence et réactivation du virus de l’herpès simplex de type 1 (HSV-1)

“…HSV-1 exprime au moins 16 miARN dont 8 (dénom-més H1-H8) sont localisés dans la région LAT [23] et sont exprimés pendant la latence. Les miARN H2, H4 et H6 inhibent respectivement l'expression d'ICP0, de la protéine 34.5 -qui joue un rôle critique dans l'inhibition des réponses cellulaires antivirales -et de la protéine ICP4 -un activateur de la transcription des gènes précoces et tardifs [23,24] (Figure 3). Il paraît donc assez plausible que l'action de ces miARN explique, au moins en partie, le rôle répresseur des LAT.…”

Interplay Between HPV Oncoproteins and MicroRNAs in Cervical Cancer

“…Keeping in view the immense impact of microRNAs expressional profile in cancer biology, conducted surveys on expressional patterns of miRNAs in cervical cancer suggested that beyond HPV, microRNAs play a major role in cervical cancer pathogenesis and progression (Reshmi and Pillai 2008). Micro-RNA expression profile in cervical cancer cell lines found that of 174 miRNAs which could be grouped into 46 different miRNA species, miR-21, miR-24, miR-27a, and miR-205 were most abundant in cervical cancer or cervical intraepithelial neoplasia derived cell lines (Wang et al, 2008). MicroRNA array analyses for age-matched normal cervix and cervical cancer tissues, in combination with Northern blot verification identified deregulated miRNAs in cervical cancer tissues.…”

“…Deletions or mutations in miRNA genes, as well as aberrant expression of oncogenic or tumor-suppressive miRNAs, are common in human cancers (Calin and Croce 2006;Wang et al 2008), but the causes for their aberrant expression are poorly understood. Although many human viruses produce their own viral miRNAs in the course of virus infection (Tang S et al, 2008& Umbach et al 2008, but recently various studies reported on viral proteins regulation of cellular miRNA expression.…”

Non-Coding RNAs: A Dynamic and Complex Network of Gene Regulation

“…The herpesvirus ICP34.5 protein promotes replication of the virus in neuronal cells in vivo. miR-I derived from HSV-1 has been shown to reduce the protein expression level of ICP34.5 in HSV-1-infected cells [90]. Hypothesized that the control of ICP34.5 expression in individual infected neurons by these microRNAs may affect their virulence or latency in the host.…”