Average levels (Ct-values, SD indicated by error bars) of transcripts 3' of intronic HERV-W elements and their corresponding genes as determined by real-time PCR. Comparison of expression levels between proviral (n = 7) and pseudoelements (n = 7), as well as comparison of expression levels between the genes into which these elements are integrated. Expression levels of transcripts encoding syncytin is shown as a reference (A). Levels of transcripts 5' and 3' of proviral elements (n = 3) or pseudoelements (n = 3) (B). Levels of transcripts 3' of proviral elements (n = 7) and solo LTRs (n = 6) (C). Levels of transcripts 3' of proviral HERV-W elements with a single (n = 3), dual LTRs (n = 4) and 3' of solo LTRs (n = 6). Expression levels of the genes into which these elements are integrated are also indicated (D). Statistical significance is indicated by *= p < 0.05, **= p < 0.01, ***= p < 0.001.