SP3, also named as transcription factor Sp3, is a 781 amino acid protein, which contains 3 C2H2-type zinc fingers and belongs to the Sp1 C2H2-type zinc-finger protein family. SP3 localizes to the nuclear periphery and in nuclear dots when sumoylated. Some localization in PML nuclear bodies. SP3 is acetylated by histone acetyltransferase p300, deacetylated by HDACs and sumoylated on all isoforms. Sumoylated on 2 sites in longer isoforms with Lys-551 being the major site. Sumoylation at this site promotes nuclear localization to the nuclear periphery, nuclear dots and PML nuclear bodies. Sumoylation on Lys-551 represses the transactivation activity, except for the largest isoform, L-Sp3, which has little effect on transactivation. Alternate sumoylation and acetylation at Lys-551 also control transcriptional activity. There exits tow modified isoform and molecular weight of those are 70 kda and 115 kda.