Figure 4. The human genome encodes a HERV-T Env ORF that does not function as a retroviral envelope.

(A) Infectiousness of MLV particles pseudotyped with untagged or C-terminally HA-tagged ancHTenv or hsaHTenv (Mean ± SD, n = 3 replicates, one of two experiments). (B) Western blot analyses (α-CA and α-HA) of cell lysates and MLV virions generated following expression of C-terminally HA-tagged ancHTenv or hsaHTenv M: markers. (C) Examples of cell fusion in 293T cell cultures expressing ancHTenv or hsaHTenv linked to IRES-GFP. Scale bar = 100 μm. (D) Percentage of GFP+ multinucleated cells (>5 nuclei/cell) in 293T cell cultures expressing ancHTenv or hsaHTenv linked to IRES-GFP (Mean ± SD, n = 3 groups of ten microscopic fields, one of two experiments) Blue: DAPI. (E) Alignment of ancHTenv and intact or nearly intact HERV-T Env protein sequences encoded by hominid genomes, proximal to the furin cleavage site. See also Figure 4—figure supplement 1.

DOI: http://dx.doi.org/10.7554/eLife.22519.012

Figure 4—figure supplement 1. Effects of mutations at the furin cleavage site on ancHTenv and hsaHTenv processing.

Western blot (anti-CA and anti-HA) analyses of cell lysates and virions following expression of MLV Gag-Pol and HA-tagged ancHTenv, hsaHTenv, or furin cleavage site-modified derivatives. AncHTenv-Furin^Mut contains the furin cleavage site residues from hsaHTenv. HsaHTenv-Furin^Fix contains the furin cleavage site residues from ancHTenv. M= molecular weight markers.

DOI: http://dx.doi.org/10.7554/eLife.22519.013