Natural antisense transcripts are detected in different cell lines and tissues of cats infected with feline immunodeficiency virus

Transcription of retroviruses is initiated at the U3-R region boundary in the integrated provirus and continues unidirectionally to produce genomic and mRNA products of positive polarity. Several studies have recently demonstrated the existence of naturally occurring protein-encoding transcripts of negative polarity in complex retroviruses. We report here on the identification of transcripts of negative polarity in simple murine leukemia virus (MLV). In T-cell and B-cell lymphomas induced by SL3-3 and Akv MLV, antisense transcripts initiated in the U3 region of the proviral 5 long terminal repeat (LTR) and continued into the cellular proto-oncogenes Jdp2 and Bach2 to create chimeric transcripts consisting of viral and host sequence. The phenomenon was validated in vivo using a knock-in mouse model homozygous for a single LTR at a position known to activate Nras in B-cell lymphomas. A 5 rapid amplification of cDNA ends (RACE) analysis indicated a broad spectrum of initiation sites within the U3 region of the 5 LTR. Our data show for the first time transcriptional activity of negative polarity initiating in the U3 region of simple retroviruses and suggest a novel mechanism of insertional activation of host genes. Elucidation of the nature and potential regulatory role of 5 LTR antisense transcription will be relevant to the design of therapeutic vectors and may contribute to the increasing recognition of pervasive eukaryotic transcription.The first base of the R region in the 5Ј long terminal repeat (LTR) defines the main transcription initiation site of retroviruses. In simple retroviruses, two major RNA species are produced by the actions of the cellular RNA polymerase II: an unspliced transcript, which serves as a template for translation of the viral genes gag and pol as well as for genomic RNA in progeny viruses, and a singly spliced transcript, which allows for production of appropriate levels of env mRNA. In addition to these common species, viral mRNA generated from the usage of an alternative splice donor site and the canonical env acceptor site has been described for Friend and Moloney murine leukemia viruses (MLVs) (11). Also, we have recently identified in Akv MLV an alternative exon generated from usage of cryptic splice acceptor and donor sites (45).

Section: Discussionsupporting

confidence: 88%

mentioning

confidence: 99%

Antisense Transcription in Gammaretroviruses as a Mechanism of Insertional Activation of Host Genes

Rasmussen

Ballarín-González

Liu

et al. 2010

“…One model would be that Rev and the RRE allow the target/antisense RNA complex to be exported to the cytoplasm, where the antisense RNA functions to inhibit protein production. Intriguingly, there have been several reports that some of the more complex retroviruses produce natural antisense transcripts (5,7,37,45,50). The best characterized of these RNAs in HIV-1 appears to initiate from multiple transcription start sites 5Ј of the 3Ј LTR and extend into the pol region, where a novel polyadenylation site has recently been described (37).…”

Section: Downloaded Frommentioning

confidence: 99%

Trafficking through the Rev/RRE Pathway Is Essential for Efficient Inhibition of Human Immunodeficiency Virus Type 1 by an Antisense RNA Derived from the Envelope Gene

Ward

Rekosh

Hammarskjöld

2009

A human immunodeficiency virus type 1 (HIV-1)-based vector expressing an antisense RNA directed against HIV-1 is currently in clinical trials. This vector has shown a remarkable ability to inhibit HIV-1 replication, in spite of the fact that therapeutic use of unmodified antisense RNAs has generally been disappointing. To further analyze the basis for this, we examined the effects of different plasmid-based HIV-1 long-terminalrepeat-driven constructs expressing antisense RNA to the same target region in HIV-1 but containing different export elements. Two of these vectors were designed to express antisense RNA containing either a Rev response element (RRE) or a Mason-Pfizer monkey virus (MPMV) constitutive transport element (CTE). In the third vector, no specific transport element was provided. Efficient inhibition of HIV-1 virus production was obtained with the RRE-driven antisense RNA. This construct also efficiently inhibited p24 production from a pNL4-3 provirus that used the MPMV CTE for RNA export. In contrast, little inhibition was observed with the constructs lacking an RRE. Furthermore, when the RRE-driven antisense RNA was redirected to the Tap/Nxf1 pathway, utilized by the MPMV CTE, through the expression of a RevM10-Tap fusion protein, the efficiency of antisense inhibition was greatly reduced. These results indicate that efficient inhibition requires trafficking of the antisense RNA through the Rev/RRE pathway. Mechanistic studies indicated that the Rev/RRE-mediated inhibition did not involve either nuclear retention or degradation of target mRNA, since target RNA was found to export and associate normally with polyribosomes. However, protein levels were significantly reduced. Taken together, our results suggest a new mechanism for antisense inhibition of HIV mediated by Rev/RRE.

“…Antisense transcription has also been suggested in other retroviruses like HIV-1 (2,8,9,27,33,36,44,48). We have recently demonstrated that antisense transcription could be detected in HTLV-2 and that the encoded antisense protein of HTLV-2 (APH-2) shares a Tax-inhibiting activity like HBZ (21).…”

mentioning

confidence: 93%

Human T-Cell Lymphotropic Virus Type 3 (HTLV-3)- and HTLV-4-Derived Antisense Transcripts Encode Proteins with Similar Tax-Inhibiting Functions but Distinct Subcellular Localization

Larocque

Halin

Marriott

et al. 2011