Sequence Analysis of Porcine Endogenous Retrovirus Long Terminal Repeats and Identification of Transcriptional Regulatory Regions

Evidence and Consequence of Porcine Endogenous Retrovirus Recombination

“…1) would be a major determinant. However, previous studies have shown that PERV-C LTR (found in A14/220 and PERV-NIH) has a similar or lesser level of activity in human cells compared to those of prototype PERV-A or PERV-B (found in Ap60) (38,53). Our infectivity analyses showed that the LTR has only minor, if any, effects on the titer difference, consistent with previous LTR studies (Fig.…”

“…In contrast, PERV-B sequences are conserved all along the genome, apart from some differences shown as troughs in the U3 region due to different numbers of enhancer repeats (Fig. 2, bottom panel) (38,51,53). There is no variability bias toward specific genes or genetic elements, indicating no evidence of recombination in recently active PERV using PERV-B receptors.…”

Evolutionary Spread and Recombination of Porcine Endogenous Retroviruses in the Suiformes

“…PERV-A and PERV-B proviruses demonstrate LTRs that harbor distinct 39-bp repeats in U3 which enable high transcription levels and adaptation to new host cells by multimerization of these repeats, with the transcriptional activity being generally stronger if more repeats are present. On the other hand, PERV-A and PERV-C were found to display repeatless LTRs (37,47). Although sequences homologous to the 39-bp repeat are present in these LTRs, they are not organized in a repetitive manner and do not show multimerization as a response to replication cycles in their hosts.…”

“…There are only minor genetic differences between the classes, being most prominent in the receptor-binding domain of the Env protein. In addition, there are two different types of long terminal repeats (LTRs) that significantly affect the replication properties of single viruses (37,47) through binding of transcription factor NF-Y (36). PERV-A and PERV-B proviruses demonstrate LTRs that harbor distinct 39-bp repeats in U3 which enable high transcription levels and adaptation to new host cells by multimerization of these repeats, with the transcriptional activity being generally stronger if more repeats are present.…”

Methods and Tools for Detection and Evaluation of the Risks of Porcine Endogenous Retrovirus in Porcine to Human Xenotransplantation

“…Therefore, several studies have evaluated the influence of variant sequences in the U3 region on the level of gene expression for PERV. While our own study did not show significant differences in expression in different cell lines tested for LTRs derived from PERV-A, -B, or -C, we did see a slightly lower level of expression with a chimeric LTR called PERV-NIH and all LTRs tested showed lower expression levels in ST-IOWA pig cells compared to other cell lines examined (Wilson, Laeeq et al 2003). In other studies, it has been shown that the level of PERV expression in permissive cells is associated with the copy number of a 39 base pair (bp) repeat in the PERV LTR U3 region (Scheef, Fischer et al 2001).…”