Abstract:

Objective To investigate the mechanism by which the aberrant fusion protein, PML/RARα, transcriptionally regulates GADD45A in acute promyelocytic leukemia (APL) cells. Methods ChIP-PCR was employed to study the enrichment of PML/RARα at the intron 3 of GADD45A. Real-Time PCR was conducted to investigate whether the ectopic expression of PML/RARα could impact the mRNA level of GADD45A gene in PR9 cell line. Eucaryotic expression vector was utilized to overexpress PML/RARα and p53 protein in H1299 cells, in order to investigate the co-regulation relationship between PML/RARα and p53 on GADD45A gene. Results ChIP-PCR revealed that the specific PML/RARα antibody could enrich the DNA segment of intron 3 of GADD45A gene compared to the negtive results of non-specific normal IgG, which indicated that PML/RARα could bind to the intron 3 of GADD45A. In PR9 cells, the expression of PML/RARα exhibited significant negtive correlation with GADD45A mRNA expression. PML/RARα could inhibit the transcriptional activity of p53 on GADD45A in H1299 cells (P<0.01). Conclusion PML/RARα can bind to the intron 3 of GADD45A gene. GADD45A is also the target of p53 protein, and PML/RARα can inhibit GADD45A expression and interrupt p53 dependent transcriptional effect of GADD45A gene.

Key words: PML/RARα, GADD45A, p53, acute promyelocytic leukemia