Long non-coding RNAs (lncRNAs) play critical roles in diverse cellular processes; however, their involvement in many critical aspects of the immune response including the interferon (IFN) response remains poorly understood. To address this gap, we compared the global gene expression pattern of primary human hepatocytes before and at three time points after treatment with IFN-α. Among ∼200 IFN-induced lncRNAs, one transcript showed ∼100-fold induction. This RNA, which we named lncRNA-CMPK2, was a spliced, polyadenylated nuclear transcript that was induced by IFN in diverse cell types from human and mouse. Similar to protein-coding IFN-stimulated genes (ISGs), its induction was dependent on JAK-STAT signaling. Intriguingly, knockdown of lncRNA-CMPK2 resulted in a marked reduction in HCV replication in IFN-stimulated hepatocytes, suggesting that it could affect the antiviral role of IFN. We could show that lncRNA-CMPK2 knockdown resulted in upregulation of several protein-coding antiviral ISGs. The observed upregulation was caused by an increase in both basal and IFN-stimulated transcription, consistent with loss of transcriptional inhibition in knockdown cells. These results indicate that the IFN response involves a lncRNA-mediated negative regulatory mechanism. lncRNA-CMPK2 was strongly upregulated in a subset of HCV-infected human livers, suggesting a role in modulation of the IFN response in vivo.

Many long non-coding RNAs (lncRNAs) are expressed in cells but only a few have been well characterized. In these cases, lncRNAs have been shown to be key regulators of several cellular processes. Therefore, there is a great need to understand the function of more lncRNAs and their regulation in response to stimuli. Interferon (IFN) is a key molecule in the cellular antiviral response. IFN binding to its receptor activates transcription of several IFN-stimulated genes (ISGs) that function as potent antivirals. In addition, several ISGs are positive or negative regulators of the IFN pathway. This is essential to ensure a strong antiviral response and a later return of the cell to homeostasis. As the ISGs described to date are coding genes, we sought to determine whether IFN also regulates the expression of long non-coding ISGs. To this aim, we used RNA sequencing to analyze the transcriptome of control and HuH7 cells treated with IFNα2. The results show that IFN-treatment regulates the expression of several unknown non-coding transcripts. We have validated two lncRNAs upregulated after treatment with different doses of type I IFNα2 in different cells or with type III IFNλ. These lncRNAs were also induced by influenza and vesicular stomatitis virus mutants unable to block the IFN response, but not by several wild-type lytic viruses tested. These lncRNA genes were named lncISG15 and lncBST2 as they are located close to ISGs ISG15 and BST2, respectively. Interestingly, inhibition experiments showed that lncBST2 is a positive regulator of BST2. Therefore lncBST2 has been renamed BISPR, from BST2 IFN-stimulated positive regulator. Our results may have therapeutic implications as lncBST2/BISPR, but also lncISG15 and their coding neighbors, are increased in cells infected with hepatitis C virus and in the liver of infected patients. These results allow us to hypothesize that several lncRNAs could be activated by IFN to control the potency of the antiviral IFN response.

The role of long noncoding RNAs (lncRNAs) in viral infection is poorly studied. We have identified hepatitis C virus (HCV)-Stimulated lncRNAs (CSRs) by transcriptome analysis. Interestingly, two of these CSRs (PVT1 and UCA1) play relevant roles in tumorigenesis, providing a novel link between HCV infection and development of liver tumors. Expression of some CSRs seems induced directly by HCV, while others are upregulated by the antiviral response against the virus. In fact, activation of pathogen sensors induces the expression of CSR32/EGOT. RIG-I and the RNA-activated kinase PKR sense HCV RNA, activate NF-jB and upregulate EGOT. EGOT is increased in the liver of patients infected with HCV and after infection with influenza or Semliki Forest virus (SFV). Genome-wide guilt-by-association studies predict that EGOT may function as a negative regulator of the antiviral pathway. Accordingly, EGOT depletion increases the expression of several interferon-stimulated genes and leads to decreased replication of HCV and SFV. Our results suggest that EGOT is a lncRNA induced after infection that increases viral replication by antagonizing the antiviral response.

Interferons (IFNs) are key players in the antiviral response. IFN sensing by the cell activates transcription of IFN-stimulated genes (ISGs) able to induce an antiviral state by affecting viral replication and release. IFN also induces the expression of ISGs that function as negative regulators to limit the strength and duration of IFN response. The ISGs identified so far belong to coding genes. However, only a small proportion of the transcriptome corresponds to coding transcripts and it has been estimated that there could be as many coding as long non-coding RNAs (lncRNAs). To address whether IFN can also regulate the expression of lncRNAs, we analyzed the transcriptome of HuH7 cells treated or not with IFNα2 by expression arrays. Analysis of the arrays showed increased levels of several well-characterized coding genes that respond to IFN both at early or late times. Furthermore, we identified several IFN-stimulated or -downregulated lncRNAs (ISRs and IDRs). Further validation showed that ISR2, 8, and 12 expression mimics that of their neighboring genes GBP1, IRF1, and IL6, respectively, all related to the IFN response. These genes are induced in response to different doses of IFNα2 in different cell lines at early (ISR2 or 8) or later (ISR12) time points. IFNβ also induced the expression of these lncRNAs. ISR2 and 8 were also induced by an influenza virus unable to block the IFN response but not by other wild-type lytic viruses tested. Surprisingly, both ISR2 and 8 were significantly upregulated in cultured cells and livers from patients infected with HCV. Increased levels of ISR2 were also detected in patients chronically infected with HIV. This is relevant as genome-wide guilt-by-association studies predict that ISR2, 8, and 12 may function in viral processes, in the IFN pathway and the antiviral response. Therefore, we propose that these lncRNAs could be induced by IFN to function as positive or negative regulators of the antiviral response.

Long Non-Coding RNAs (lncRNAs) are functional RNAs longer than 200 nucleotides in length. Several lncRNAs are involved in cell proliferation and are deregulated in several human tumors. Few lncRNAs have been described to play a role in Acute Lymphoblastic Leukemia (ALL). In this study, we carried out a genome wide lncRNA expression profiling in ALL samples and peripheral blood samples obtained from healthy donors. We detected 43 lncRNAs that were aberrantly expressed in ALL. Interestingly, among them, linc-PINT showed a significant downregulation in T and B-ALL. Re-expression of linc-PINT in ALL cells induced inhibition of leukemic cell growth that was associated with apoptosis induction and cell cycle arrest in G2/M phase. linc-PINT induced the transcription of HMOX1 which reduced the viability of ALL cells. Intriguingly, we observed that treatment with anti-tumoral epigenetic drugs like LBH-589 (Panobinostat) and Curcumin induced the expression of linc-PINT and HMOX1 in ALL. These results indicate that the downregulation of linc-PINT plays a relevant role in the pathogenesis of ALL, and linc-PINT re-expression may be one of the mechanisms exerted by epigenetic drugs to reduce cell proliferation in ALL.