Human Blimp-1 is a 91kD zinc-finger transcriptional repressor that promotes B cell maturation into plasma cells. It is 789 amino acids (aa) in length, and contains an N-terminal S-E-T domain (aa64-170) and four C-terminal C2H2-type zinc-finger motifs (aa539-645). The SET domain interacts with chromatin modifers, while the zinc fingers bind to DNA. There is one 80kD, 691aa alternate splice form that utilizes an intenal start site. This results in a substitution of three aa for the first 101 aa of the long form, and the loss of the SET domain. At least 10 mutations exist, resulting in proteins of 61-603 aa in length. Over aa 667-789, human Blimp-1 is 89% aa identical to mouse Blimp-1.