Apolipoprotein A-1 (APOA1) is the major protein component of high-density lipoprotein (HDL) in plasma. We have identified an endogenously expressed long non-coding natural antisense transcript, APOA1-AS, which acts as a negative transcriptional regulator of APOA1, both in vitro and in vivo. Inhibition of APOA1-AS in cultured cells resulted in the increased expression of APOA1, and two neighboring genes in the APO cluster. Chromatin immunoprecipitation (ChIP) analyses of a ~50Kb chromatin region flanking the APOA1 gene demonstrated that APOA1-AS can modulate distinct histone methylation patterns that mark active and/or inactive gene expression, through the recruitment of histone-modifying enzymes. Targeting APOA1-AS using short antisense oligonucleotides also enhanced APOA1 expression in both human and monkey liver cells, and induced an increase in hepatic RNA and protein expression in African green monkeys. The results presented here further highlight the significant local modulatory effects of long non-coding antisense RNAs, and demonstrate the therapeutic potential of manipulating the expression of these transcripts both in vitro and in vivo.

Dravet syndrome is a devastating genetic brain disorder caused by heterozygous loss-of-function mutation in the voltage-gated sodium channel gene SCN1A. There are currently no treatments, but the upregulation of SCN1A healthy allele represents an appealing therapeutic strategy. In this study we identified a novel, evolutionary conserved mechanism controlling the expression of SCN1A that is mediated by an antisense non-coding RNA (SCN1ANAT). Using oligonucleotide-based compounds (AntagoNATs) targeting SCN1ANAT we were able to induce specific upregulation of SCN1A both in vitro and in vivo, in the brain of Dravet knock-in mouse model and a non-human primate. AntagoNAT-mediated upregulation of Scn1a in postnatal Dravet mice led to significant improvements in seizure phenotype and excitability of hippocampal interneurons. These results further elucidate the pathophysiology of Dravet syndrome and outline a possible new approach for the treatment of this and other genetic disorders with similar etiology.

Mother-to-child transmission can occur in utero, mainly intrapartum and postpartum in case of breastfeeding. In utero transmission is highly restricted and results in selection of viral variant from the mother to the child. We have developed an in vitro system that mimics the interaction between viruses, infected cells present in maternal blood, and the trophoblast, the first barrier protecting the fetus. Trophoblastic BeWo cells were grown as a tight polarized monolayer in a two-chamber system. Cell-free virions applied to the apical pole neither crossed the barrier nor productively infected BeWo cells. In contrast, apical contact with human immunodeficiency virus (HIV)-infected peripheral blood mononuclear cells (PBMCs) resulted in transcytosis of infectious virus across the trophoblastic monolayer and in productive infection correlating with the fusion of HIV-infected PBMCs with trophoblasts. We showed that viral variants are selected during these two steps and that in one case of in utero transmission, the predominant maternal viral variant characterized after transcytosis was phylogenetically indistinguishable from the predominant child's virus. Hence, the first steps of transmission of HIV-1 in utero appear to involve the interaction between HIV type 1-infected cells and the trophoblastic layer, resulting in the passage of infectious HIV by transcytosis and by fusion/infection, both leading to a selection of virus quasispecies.

Hepatitis C virus (HCV), the global leading cause of chronic liver disease, has a positive-sense, ssRNA genome that encodes a large polyprotein. HCV polyprotein translation is initiated by an internal ribosome-entry site (IRES) located at the 59 end of the viral genome, in a cap-independent manner, but the regulatory mechanism of this process remains poorly understood. In this study, we characterized the effect of HCV nonstructural proteins on HCV IRES-directed translation in both HCV replicon cells and transiently transfected human liver cells expressing HCV nonstructural proteins. Using bicistronic reporter gene constructs carrying either HCV or other viral IRES sequences, we found that the HCV IRES-mediated translation was specifically upregulated in HCV replicon cells. This enhancement of HCV IRES-mediated translation by the replicon cells was inhibited by treatment with either type I interferon or ribavirin, drugs that perturb HCV genome replication, suggesting that the enhancement is probably due to HCV-encoded protein function(s). Reduced phosphorylation levels of both eIF2a and eIF4E were observed in the replicon cells, which is consistent with our previous findings and indicates that the NS5A nonstructural protein may be involved in the regulatory mechanism(s). Indeed, transient expression of NS5A or NS4B in human liver cells stimulated HCV IRES activity. Interestingly, mutation in the ISDR of NS5A perturbed this stimulation of HCV IRES activity. All these results suggest, for the first time, that HCV nonstructural proteins preferentially stimulate the viral cap-independent, IRES-mediated translation. INTRODUCTIONHepatitis C virus (HCV) is the leading cause of chronic liver disease globally and is estimated to infect about 170 million people around the world (Alter, 1997). Chronic HCV infection frequently leads to liver fibrosis and cirrhosis, and is associated with the occurrence of hepatocellular carcinoma (Hoofnagle, 1997). There is no vaccine available for HCV, and the current therapies, either interferon (IFN)-a monotherapy, or a combination of IFN-a and ribavirin, have been unable to eliminate HCV replication in the majority of patients (Moradpour & Blum, 1999). However, the molecular mechanisms of HCV replication and persistence remain poorly characterized, since neither an adequate animal model, nor an efficient cell culture system for HCV infection and replication, are currently available (Gale & Beard, 2001). Further studies aiming at dissecting the molecular aspects of HCV life-cycle are thus of particular importance.A Flaviviridae family member, HCV possesses a positivesense, ssRNA genome of about 9600 nucleotides (Reed & Rice, 2000). The HCV genome consists of highly conserved 59-and 39-noncoding regions (NCR), and a large open reading frame (ORF) that encodes a polyprotein of approximately 3010 amino acids. The polyprotein is processed co-and post-translationally by both host and viral proteases into at least 10 structural (core, E1, E2 and p7) and nonstructural (NS) proteins (NS2, NS3, NS...