SP1 and systemic lupus erythematosus: Histone deacetylase inhibitors (HDACi), such as trichostatin (TSA), repress IRF5 and hence have therapeutic potential in patients with SLE. TSA-mediated inhibition of IRF5 binding to RNA polymerase II, HDAC3, DNA Sp1, and p300 in children with SLE suggests that SLE is associated with DNA degradation abnormalities and elimination defects (23).