[Effect of MLL-AF9 fusion gene silence of acute monocytic leukemia cell line THP-1 on cyclin-dependent kinase inhibitor p27 expression].

OBJECTIVE

To explore the effect of MLL-AF9 fusion gene silence on p27 expression and transcription regulation in THP-1 cells.

METHODS

Small interference RNA (siRNA) fragments targeting THP-1 cells specific MLL-AF9 fusion gene were designed and constructed, and transfected into THP-1 by lipofectamine. Flow cytometry was used to detect siRNA transfection efficiency. The level of MLL-AF9 mRNA expression was examined by RT-PCR and the expression of MLL-AF9 and p27 protein was detected by Western blot. Chromatin immunoprecipitation (ChIP) assay was used to confirm whether MLL-AF9 binds to the p27 promoter in THP-1 cell.

RESULTS

SiRNA transfection efficiency was (69.1 +/- 1.8)%. The level of p27 expression was up-regulated at both mRNA [(0.84 +/- 0.12) vs (0.35 +/- 0.03) of control group] and protein levels after MLL-AF9 expression was significantly inhibited in siRNA-transfected cells (0.31 +/- 0.07) compared with that in the controls (1.25 +/- 0.13) (P<0.01). MLL-AF9 fusion protein bond to DNA fragment of p27 gene promoter region in THP-1 cell.

CONCLUSION

MLL-AF9 fusion gene silence up-regulates p27 gene expression, and the mechanism maybe the recovery of p27 gene expression due to MLL-AF9 fusion protein binding to p27 promoter.