FrRUNT sequence detail, showing its compact organization and its interlocking with the SUPT3H gene. The two genes are disposed in opposite orientations. The inverted lettering for SUPT3H denotes translation from the reverse strand. The two putative promoters and the extent of the runt domain (RD) are indicated; x1–x6 denote the six exons. The black triangle points at the asparagine residue absent from all previously known runt domain proteins.