Concomitantly, both UV-mediated DNA damage (Fig. 6B) and direct challenge with DNA fragments (Fig. 6D) induced the expression of E2F1, DP-1, c-Jun, and c-Fos with the upregulation of TREX1 in RA-FLSs in a time-dependent manner. Here, E2F1 is linked to rheumatoid arthritis.