High Mobility Group Protein B3 (HMGB3) belongs to the HMGB family. Members of the HMG box subfamily are thought to be have an important role in DNA replication, nucleosome assembly and transcription. HMGB3 binds preferentiallly single-stranded DNA and unwinds double stranded DNA. HMGB3 consists of 200 amino acids and is localized to the cell nucleus. It contains two HMG box DNA-binding domain. HMGB3 binds preferentially single-stranded DNA and unwinds double stranded DNA.