FXN and Friedreich ataxia: Moreover, a study by the Wade-Martins group demonstrated that the inhibition of SUV4-20H1 and SUV4-20H2 methyltransferase activity by the compound A-196 and its derivatives can reduce H4K20me2/3 and stimulate FXN gene expression at both the mRNA and protein levels in FRDA patient fibroblasts [33], providing evidence that the suppression of H4K20me2/3 may also lead to open chromatin.