Ferrucci P F, Grignani F, Pearson M, Fagioli M, Nicoletti I, Pelicci P G
European Institute of Oncology, Department of Experimental Oncology, 20141 Milan, Italy.
Proc Natl Acad Sci U S A. 1997 Sep 30;94(20):10901-6. doi: 10.1073/pnas.94.20.10901.
PML/RARalpha is the abnormal protein product generated by the acute promyelocytic leukemia-specific t(15;17). Expression of PML/RARalpha in hematopoietic precursor cell lines induces block of differentiation and promotes survival. We report here that PML/RARalpha has a potent growth inhibitory effect on all nonhematopoietic cell lines and on the majority of the hematopoietic cell lines tested. Inducible expression of PML/RARalpha in fibroblasts demonstrated that the basis for the growth suppression is induction of cell death. Deletion of relevant promyelocytic leukemia (PML) and retinoic acid receptor (RARalpha) domains within the fusion protein revealed that its growth inhibitory effect depends on the integrity of the PML aminoterminal region (RING, B1, B2, and coiled coil regions) and the RARalpha DNA binding region. Analysis of the nuclear localization of the same PML/RARalpha deletion mutants by immunofluorescence and cell fractionation revealed that the biological activity of the fusion protein correlates with its microspeckled localization and its association to the nuclear matrix. The PML aminoterminal region, but not the RARalpha zinc fingers, is required for the proper nuclear localization of PML/RARalpha. We propose that the matrix-associated microspeckles are the active sites of PML/RARalpha and that targeting of RARalpha sequences to this specific nuclear subdomain through PML sequences is crucial to the activity of the fusion protein on survival regulation.
PML/RARα 是急性早幼粒细胞白血病特异性 t(15;17) 产生的异常蛋白产物。PML/RARα 在造血前体细胞系中的表达诱导分化阻滞并促进存活。我们在此报告，PML/RARα 对所有非造血细胞系以及大多数测试的造血细胞系具有强大的生长抑制作用。在成纤维细胞中可诱导表达 PML/RARα 表明生长抑制的基础是细胞死亡的诱导。融合蛋白中相关早幼粒细胞白血病（PML）和视黄酸受体（RARα）结构域的缺失表明其生长抑制作用取决于 PML 氨基末端区域（RING、B1、B2 和卷曲螺旋区域）和 RARα DNA 结合区域的完整性。通过免疫荧光和细胞分级分离对相同 PML/RARα 缺失突变体的核定位分析表明，融合蛋白的生物学活性与其微斑点定位及其与核基质的关联相关。PML/RARα 的正确核定位需要 PML 氨基末端区域，而不是 RARα 锌指。我们提出，与基质相关的微斑点是 PML/RARα 的活性位点，并且通过 PML 序列将 RARα 序列靶向到这个特定的核亚结构域对于融合蛋白在存活调节方面的活性至关重要。
