Department of Medicine, Baylor College of Medicine, Houston, TX, USA.
Blood. 2010 Jan 21;115(3):643-52. doi: 10.1182/blood-2009-07-232652. Epub 2009 Nov 17.
PRKAR1A (R1A)-retinoic acid receptor-alpha (R1A-RARalpha) is the sixth RARalpha-containing fusion protein in acute promyelocytic leukemia (APL). Using the murine bone-marrow retroviral transduction/transformation assay, we showed that R1A-RARalpha fusion protein could transform bone-marrow progenitor/stem cells. In gel-shift assays, R1A-RARalpha was able to bind to a panel of retinoic acid response elements both as a homodimer and as a heterodimer with RXRalpha, and demonstrated distinct DNA-binding characteristics compared with wild-type RARalpha/RXRalpha or other X-RARalpha chimeric proteins. The ratio of R1A-RARalpha to RXRalpha proteins affected the retinoic acid response element interaction pattern of R1A-RARalpha/RXRalpha complexes. Studies comparing R1A-RARalpha with R1A-RARalpha(DeltaRIIa) demonstrated that the RIIa protein interaction domain located within R1A was responsible for R1A-RARalpha homodimeric DNA binding and interaction with wild-type R1A protein. However, the RIIa domain was not required for R1A-RARalpha-mediated transformation because its deletion in R1A-RARalpha(DeltaRIIa) did not compromise its transformation capability. In contrast, introduction of point mutations within the RARalpha portion of either R1A-RARalpha or R1A-RARalpha(DeltaRIIa), previously demonstrated to eliminate RXRalpha interaction or treatment of transduced cells with RXRalpha shRNA or a RXRalpha agonist, reduced transformation capability. Thus, leukemic transformation by APL fusion protein PRKAR1A-RARalpha is critically dependent on RXRalpha, which suggests RXRalpha is a promising target for APL.
PRKAR1A（R1A）-视黄酸受体-α（R1A-RARα）是急性早幼粒细胞白血病（APL）中第六种含有 RARα 的融合蛋白。使用小鼠骨髓逆转录病毒转导/转化测定法，我们表明 R1A-RARα 融合蛋白可以转化骨髓祖细胞/干细胞。在凝胶迁移分析中，R1A-RARα 能够作为同源二聚体和与 RXRα 的异源二聚体结合到一组视黄酸反应元件上，并且与野生型 RARα/RXRα 或其他 X-RARα 嵌合蛋白相比，表现出不同的 DNA 结合特征。R1A-RARα 与 RXRα 蛋白的比例影响 R1A-RARα/RXRα 复合物对视黄酸反应元件的相互作用模式。将 R1A-RARα 与 R1A-RARα(ΔRIIa)进行比较的研究表明，位于 R1A 内的 RIIa 蛋白相互作用域负责 R1A-RARα 同源二聚体 DNA 结合以及与野生型 R1A 蛋白的相互作用。然而，RIIa 结构域对于 R1A-RARα 介导的转化不是必需的，因为其在 R1A-RARα(ΔRIIa)中的缺失并没有损害其转化能力。相比之下，先前证明消除 RXRα 相互作用的 R1A-RARα 或 R1A-RARα(ΔRIIa)中的 RARα 部分的点突变或用 RXRα shRNA 或 RXRα 激动剂处理转导细胞，降低了转化能力。因此，APL 融合蛋白 PRKAR1A-RARα 的白血病转化严重依赖于 RXRα，这表明 RXRα 是 APL 的一个有前途的靶点。
