Sun L, Crotty M L, Sensel M, Sather H, Navara C, Nachman J, Steinherz P G, Gaynon P S, Seibel N, Mao C, Vassilev A, Reaman G H, Uckun F M
Parker Hughes Cancer Center and Children's Cancer Group ALL Biology Reference Laboratory, Hughes Institute, St. Paul, Minnesota 55113, USA.
Clin Cancer Res. 1999 Aug;5(8):2112-20.
Ikaros, a zinc finger-containing DNA-binding protein, is required for normal lymphocyte development. Germ-line mutant mice that express only non-DNA binding dominant-negative "leukemogenic" Ikaros isoforms lacking critical NH2-terminal zinc fingers develop an aggressive form of T-cell leukemia. We studied Ikaros gene expression in leukemic cells from 18 children with T-cell acute lymphoblastic leukemia (T-ALL). In each of the 18 T-ALL cases as well as JK-E6-1 and MOLT-3 cell lines, we found high-level expression of dominant-negative isoforms of Ikaros with abnormal subcellular compartmentalization patterns. Nuclear extracts from these cells failed to bind to the IKAROS-specific binding sequence in DNA. PCR cloning and sequencing confirmed that JK-E6-1 and MOLT-3 cell lines as well as leukemic cells from 9 of 10 patients with T-ALL expressed dominant-negative Ikaros isoforms Ik-4, Ik-7, and Ik-8 that lack critical NH2-terminal zinc fingers. In 6 of 10 patients, we detected a specific mutation leading to an in-frame deletion of 10 amino acids (delta KSSMPQKFLG) upstream to the transcription activation domain and adjacent to the COOH-terminal zinc fingers of Ik-2, Ik-4, Ik-7, and Ik-8. Thus, children with T-ALL express high levels of dysfunctional dominant-negative Ikaros isoforms.
Ikaros是一种含锌指结构的DNA结合蛋白，是正常淋巴细胞发育所必需的。生殖系突变小鼠仅表达缺乏关键NH2末端锌指的非DNA结合显性负性“致白血病”Ikaros异构体，会发展出侵袭性T细胞白血病。我们研究了18例儿童T细胞急性淋巴细胞白血病（T-ALL）白血病细胞中的Ikaros基因表达。在18例T-ALL病例以及JK-E6-1和MOLT-3细胞系中，我们发现具有异常亚细胞定位模式的Ikaros显性负性异构体的高水平表达。这些细胞的核提取物未能与DNA中的IKAROS特异性结合序列结合。PCR克隆和测序证实，JK-E6-1和MOLT-3细胞系以及10例T-ALL患者中9例的白血病细胞表达缺乏关键NH2末端锌指的显性负性Ikaros异构体Ik-4、Ik-7和Ik-8。在10例患者中的6例中，我们检测到一个特定突变，导致在转录激活域上游且与Ik-2、Ik-4、Ik-7和Ik-8的COOH末端锌指相邻处发生10个氨基酸（δKSSMPQKFLG）的框内缺失。因此，T-ALL患儿表达高水平的功能失调显性负性Ikaros异构体。
