目的 研究异常转录因子PML/RARα对GADD45A的转录调控机制，为进一步阐释PML/RARα在急性早幼粒细胞白血病（APL）发病中的作用机制提供线索。方法 运用ChIP-PCR技术研究PML/RARα与GADD45A的结合情况；采用Real-Time PCR技术检测PR9细胞中GADD45A mRNA的表达水平，并分析其与PML/RARα融合蛋白表达的相关性；利用真核细胞表达载体在H1299细胞中过表达PML/RARα和p53蛋白，研究PML/RARα与p53对GADD45A的共调控关系。结果 PML/RARα ChIP-qPCR结果显示：PML/RARα特异性抗体能够富集GADD45A基因功能区第3个内含子区的DNA片段，而非特异性IgG不能够富集；在PR9细胞中发现GADD45A mRNA表达水平与PML/RARα蛋白的表达呈负相关，说明在PR9细胞中PML/RARα融合蛋白能够抑制GADD45A 的表达；在H1299细胞中单独转染野生型p53表达质粒后，GADD45A在mRNA水平显著上调，而共转染PML/RARα和野生型p53表达质粒后，PML/RARα能够显著抑制p53对GADD45A在mRNA水平的上调作用（P<0.01）。结论 PML/RARα能够结合在GADD45A第3个内含子区域并抑制其转录表达。GADD45A同时也是p53的靶基因，PML/RARα与p53对GADD45A有共调控关系。PML/RARα能够抑制p53对GADD45A的转录激活效应。

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.