Myeloid Leukemia Factor 1 (MLF1)

The translocation was identified in 3 t(3;5)-positive cases of AML. The MLF1 gene encodes a predicted 268-amino acid polypeptide that is 40% identical to MLF2. Expression of the mRNA was widespread but highest in testis, ovary, skeletal muscle, heart, kidney and colon. Antibodies to MLF1 detected a 31-kD protein in K562 and HEL erythroleukemia cell lines. In leukemia cells with the translocation, only a 54-kD NPM-MLF1 protein was detected.

Immunostaining showed that MLF1 occurs in the cytoplasm while the NPM-MLF1 fusion protein was targeted to the nucleus, especially the nucleolus. NPM is a nuclear protein and therefore the authors concluded that the N-terminal portion that is fused to MLF1 must carry the nuclear targeting signal.