Assuntos
Leucemia/genética , Cadeias Pesadas de Miosina/genética , Proteínas de Fusão Oncogênica/genética , Animais , Carcinogênese/genética , Subunidades alfa de Fatores de Ligação ao Core/genética , Repressão Epigenética , Heterozigoto , Camundongos , Camundongos Transgênicos , Mutação , Domínios Proteicos/genética , Transcrição GênicaRESUMO
CBFß-SMMHC (core-binding factor ß-smooth muscle myosin heavy chain), the fusion protein generated by the chromosome 16 inversion fusion gene, CBFB-MYH11, is known to initiate leukemogenesis. However, the mechanism through which CBFß-SMMHC contributes to leukemia development is not well understood. Previously, it was proposed that CBFß-SMMHC acts by dominantly repressing the transcription factor RUNX1 (Runt-related protein 1), but we recently showed that CBFß-SMMHC has activities that are independent of RUNX1 repression. In addition, we showed that a modified CBFß-SMMHC with decreased RUNX1-binding activity accelerates leukemogenesis. These results raise questions about the importance of RUNX1 in leukemogenesis by CBFß-SMMHC. To test this, we generated mice expressing Cbfb-MYH11 in a Runx1-deficient background, resulting from either homozygous Runx1-null alleles (Runx1(-/-)) or a single dominant-negative Runx1 allele (Runx1(+/lz)). We found that loss of Runx1 activity rescued the differentiation defects induced by Cbfb-MYH11 during primitive hematopoiesis. During definitive hematopoiesis, RUNX1 loss also significantly reduced the proliferation and differentiation defects induced by Cbfb-MYH11. Importantly, Cbfb-MYH11-induced leukemia had much longer latency in Runx1(+/lz) mice than in Runx1-sufficient mice. These data indicate that Runx1 activity is critical for Cbfb-MYH11-induced hematopoietic defects and leukemogenesis.
