Figure 1. Metaphase spread of an acute myeloid leukemic cell, showing a balanced translocation between chromosomes 11 (green) and 10 (pink). All other chromosomes are in blue. In this case the translocation resulted in an in-frame fusion of the 5¢ end of the MLL gene on 11q23 with the 3¢ end of the MLLT10 gene on 10p12.

Figure 2. One of the effects of chromosomal translocations involving transcription factors. Protein A has a DNA-binding domain and interacts with protein B with its interactive domain. As a result, protein C is upregulated. As the levels of protein C rise, protein D is also upregulated. Protein D docks on protein B and blocks the A–B interaction (shown by a change in the polarization of the molecule), switching the activation of protein C. As a result of a chromosomal translocation, protein A fuses to B, and B loses its docking domain, thus C becomes constitutionally upregulated.

Figure 3. Two classes of proteins are involved in the genesis of fusion genes: those that encode transcription factors involved in development (dark gray ellipses), which tend to occur in acute leukemias and sarcomas of childhood; and genes encoding tyrosine kinases (gray ellipses), which are usually associated with chronic myeloid leukemia, lymphoma and thyroid carcinomas.

Figure 4. Effect of the t(12;21) translocation. The ETV6 gene on chromosome 12p13 encodes a protein with an N-terminal dimerization motif (PNT) which acts as a repressor, a central NCOR recruiting domain and a C-terminal DNA-binding ETS domain. The RUNX1 gene on 21q22 encodes a protein with an N-terminus DNA-binding runt domain and a C-terminus transcriptional activation domain. As a result of the translocation (breakpoints are indicated by arrows), the repressor domain of ETV6 is fused to almost the whole RUNX1 molecule. The fusion gene product is able to competitively repress transcription of RUNX1 target genes. WRPY is a tetrapeptide motif.