Department of Microbiology and Immunology, School of Medicine, Temple University, Philadelphia, PA, USA.
Blood. 2011 Jul 28;118(4):1062-8. doi: 10.1182/blood-2010-09-307256. Epub 2011 Jun 7.
Chronic myeloid leukemia chronic phase (CML-CP) CD34(+) cells contain numerous DNA double-strand breaks whose unfaithful repair may contribute to chromosomal instability and disease progression to blast phase (CML-BP). These phenomena are often associated with the appearance of imatinib-resistant BCR-ABL1 kinase mutants (eg, T315I) and overexpression of BCR-ABL1. Here we show that BCR-ABL1 (nonmutated and T315I mutant) promoted RAD51 recombinase-mediated unfaithful homeologous recombination repair (HomeoRR) in a dosage-dependent manner. BCR-ABL1 SH3 domain interacts with RAD51 proline-rich regions, resulting in direct phosphorylation of RAD51 on Y315 (pY315). RAD51(pY315) facilitates dissociation from the complex with BCR-ABL1 kinase, migrates to the nucleus, and enhances formation of the nuclear foci indicative of recombination sites. HomeoRR and RAD51 nuclear foci were strongly reduced by RAD51(Y315F) phosphorylation-less mutant. In addition, peptide aptamer mimicking RAD51(pY315) fragment, but not that with Y315F phosphorylation-less substitution, diminished RAD51 foci formation and inhibited HomeoRR in leukemia cells. In conclusion, we postulate that BCR-ABL1 kinase-mediated RAD51(pY315) promotes unfaithful HomeoRR in leukemia cells, which may contribute to accumulation of secondary chromosomal aberrations responsible for CML relapse and progression.
慢性髓性白血病慢性期 (CML-CP) CD34(+) 细胞中含有许多 DNA 双链断裂，其错误修复可能导致染色体不稳定和疾病向急变期 (CML-BP) 进展。这些现象通常与出现伊马替尼耐药的 BCR-ABL1 激酶突变体（例如 T315I）和 BCR-ABL1 的过表达有关。在这里，我们表明 BCR-ABL1（未突变和 T315I 突变）以剂量依赖的方式促进 RAD51 重组酶介导的不忠实同源重组修复（HomeoRR）。BCR-ABL1 SH3 结构域与 RAD51 脯氨酸丰富区域相互作用，导致 RAD51 在 Y315 上直接磷酸化（pY315）。RAD51(pY315) 促进与 BCR-ABL1 激酶复合物的解离，迁移到核内，并增强指示重组位点的核焦点的形成。HomeoRR 和 RAD51 核焦点强烈减少由 RAD51(Y315F) 磷酸化缺失突变体。此外，模拟 RAD51(pY315) 片段的肽适体，而不是具有 Y315F 磷酸化缺失取代的片段，减少了 RAD51 焦点的形成并抑制了白血病细胞中的 HomeoRR。总之，我们假设 BCR-ABL1 激酶介导的 RAD51(pY315) 促进白血病细胞中不忠实的 HomeoRR，这可能导致负责 CML 复发和进展的继发性染色体畸变的积累。
