Recent findings indicate that hDaxx associates via its newly identified SUMO-interacting motif (SIM) with SUMOylated DNA-binding transcription factors [26], thereby recruiting proteins involved in transcriptional repression, such as histone deacetylase 1 (HDAC1) [29], HDAC2 [38], DNA methyltransferase 1 (DNMT1) [39], or ATRX (α-thalassaemia/mental retardation syndrome X-linked) [40,41], a member of the SNF2 family of chromatin remodeling enzymes, to targeted promoters. Here, HDAC1 is linked to thalassemia.