LTR promoter activity of SRLV genotype E, strain Roccaverano

Abstract

The highly divergent, small ruminant lentivirus (SRLV) genotype E Roccaverano strain has a full genome consisting of 8,418 nucleotides, which lack the entire dUTPase subunit of the pol gene, the vpr-like accessory gene, and the 71-bp repeat of the U3 region within the long terminal repeat (LTR). These deletions affect in reverse transcriptase fidelity in non-dividing cells (dUTPase and vpr-like) and in the regulation of viral replication. Surprisingly, this SRLV strain was able to replicate efficiently in non-dividing cells (i.e., blood-derived macrophages), while replication in fibroblastic-like cells was somewhat restricted. To evaluate whether this observation was due to the presence/absence of specific transcription factors within these fibroblasts, U3 transcriptional activity was measured in the different cell types and revealed that both fibroblasts and macrophages were able to activate the viral promoter in the same manner. Among the transcription factor-binding sites present within the U3 region, the highly conserved Ap4 tandem repeat was shown to be sufficient for LTR promoter activity.

Genotyping Based on the LTR Region of Small Ruminant Lentiviruses from Naturally Infected Sheep and Goats from Mexico

“…Juganaru et al [28] showed that the AP-4 sites are necessary to maintain the basal promoter activity of the LTR in synergy with the AP-1 sites, and that their absence reduces it. The TATA box is also located in the U3 region and it is an important element as a promoter of transcription.…”

Characterization of new small ruminant lentivirus subtype B3 suggests animal trade within the Mediterranean Basin

“…In order to gain some insight into the biological features of these new viral strains, the U3 region was analysed. The Fonni and Volterra strains share very similar organization of the promoter region, which contains the highly conserved AML (acute myeloid leukaemia) motif (Murphy et al , 2010) and the AP4 tandem repeat, which has been found to be necessary and sufficient for efficient transcriptional activation (Juganaru et al , 2010; Mermod et al , 1988). The tumour necrosis factor (TNF)-activated transcription site (Murphy et al , 2007) and the AP1 sequence (Gabuzda et al , 1989) were slightly heterogeneous compared with CAEV strains (data not shown).…”

Detailed analysis of the promoter activity of an attenuated lentivirus

“…This suggests, as is the case for human immunodeficiency virus (HIV-1; Duverger et al, 2013), a potential involvement of one or more of the AP-1 sites targeted, or the restored AMLa site, in promoting the establishment of latency rather than virus replication. The unique AP-4-binding site present in the LTR was described as crucial or even essential for promoter activity (Campbell & Avery, 1996;Hess et al, 1989;Juganaru et al, 2010). In our reporter gene assay, the replacement of AP-4 by the EcoRI recognition sequence had no significant influence on luciferase activity.…”