Fig. 6: Transcriptional regulation of TREX1 via E2F1 signalling and the balance of c-Jun/c-Fos.

A The expression levels of TREX1 and DP-1 in RA-FLSs overexpressing the transcription factor E2F1. RA-FLS were transfected with the E2F1 plasmid for 48 h. All samples are biologically independent, and statistical significance was calculated by one-way ANOVA, **P < 0.01 versus control groups. Data are presented as the mean ± s.e.m. from three independent experiments. B Gene expression profiles of TREX1, E2F1, DP-1, c-Jun and c-Fos in RA-FLSs exposed to UV light for different durations. C Role of E2F1 in the transcriptional regulation of TREX1 in UV-stimulated cells. RA-FLSs with siRNA-mediated E2F1 silencing were exposed to UV light for 0–15 min, and the gene expression levels of E2F1 and TREX1 were determined by RT–PCR. D Gene expression profiles of TREX1, E2F1, DP-1, c-Jun and c-Fos in RA-FLSs stimulated with DNA fragments. E Knockdown of E2F1 inhibited TREX1 activation in RA-FLSs transfected with DNA fragments. RA-FLSs with siRNA-mediated E2F1 silencing were transfected with 5 μg of DNA fragments for 48 h. F Presenescent RA-FLSs were rendered senescent by repeated passaging to late passages. Both early- and late-passage RA-FLSs were transfected with 5 μg of DNA fragments for 48 h. G Knockdown of c-Fos inhibited the activation of TREX1 in RA-FLSs transfected with DNA fragments. RA-FLSs with siRNA-mediated c-Fos silencing were transfected with 5 μg of DNA fragments for 48 h. In (B) and (D), all data were presented as the mean ± s.e.m. from three independent experiments. In (C) and (E), all samples are biologically independent, and statistical significance was calculated by t-test, *P < 0.05, **P < 0.01 between two groups. Data are presented as the mean ± s.e.m. from three independent experiments. In (F) and (G), the bar charts show the quantification of target protein expression relative to tubulin expression using ImageJ software. All samples are biologically independent, and statistical significance was calculated by t-test, **P < 0.01 between the two groups. Data are presented as the mean ± s.e.m. from three independent experiments. All samples are derived from the same experiment and the gels/blots were processed in parallel.