RESUMO
The fusion oncogene RUNX1/RUNX1T1 encodes an aberrant transcription factor, which plays a key role in the initiation and maintenance of acute myeloid leukemia. Here we show that the RUNX1/RUNX1T1 oncogene is a regulator of alternative RNA splicing in leukemic cells. The comprehensive analysis of RUNX1/RUNX1T1-associated splicing events identifies two principal mechanisms that underlie the differential production of RNA isoforms: (i) RUNX1/RUNX1T1-mediated regulation of alternative transcription start site selection, and (ii) direct or indirect control of the expression of genes encoding splicing factors. The first mechanism leads to the expression of RNA isoforms with alternative structure of the 5'-UTR regions. The second mechanism generates alternative transcripts with new junctions between internal cassettes and constitutive exons. We also show that RUNX1/RUNX1T1-mediated differential splicing affects several functional groups of genes and produces proteins with unique conserved domain structures. In summary, this study reveals alternative splicing as an important component of transcriptome re-organization in leukemia by an aberrant transcriptional regulator.
Assuntos
Processamento Alternativo , Subunidade alfa 2 de Fator de Ligação ao Core/genética , Regulação Leucêmica da Expressão Gênica , Leucemia Mieloide/genética , Proteínas de Fusão Oncogênica/genética , Proteína 1 Parceira de Translocação de RUNX1/genética , Doença Aguda , Linhagem Celular Tumoral , Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Perfilação da Expressão Gênica/métodos , Humanos , Leucemia Mieloide/patologia , Modelos Genéticos , Proteínas de Fusão Oncogênica/metabolismo , Interferência de RNA , Isoformas de RNA/genética , Isoformas de RNA/metabolismo , Proteína 1 Parceira de Translocação de RUNX1/metabolismo , Sítio de Iniciação de TranscriçãoRESUMO
The RUNX1-RUNX1T1 fusion gene, a product of the nonhomologous balanced translocation t(8;21)(q22;q22), is a complex genetic locus. We performed extensive bioinformatic analysis of transcription initiation as well as transcription termination sites in this locus and predicted a number of different RUNX1T1 transcripts. To confirm and quantify the RUNX1T1 gene expression, we analyzed samples from seven acute myeloid leukemia (AML) patients and from the Kasumi-1 cell line. We found variable activity of the four predicted RUNX1T1 promoters located downstream of the chromosome breakpoint. Nineteen alternative RUNX1T1 transcripts were identified by sequencing at least seventeen of which predictably can be translated into functional proteins. While the RUNX1T1 gene is not expressed in normal hematopoietic cells, it may participate in t(8;21)(q22;q22)-dependent leukemic transformation due to its multiple interactions in cell regulatory network particularly through synergistic or antagonistic effects in relation to activity of RUNX1-RUNX1T1 fusion gene.