| Abstract: |
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 (Δ 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. |
| Keywords: |
adult; child; clinical article; protein expression; child, preschool; dna binding protein; gene deletion; mutation; dna-binding proteins; protein conformation; lymphocyte proliferation; t-lymphocytes; protein dna binding; tumor cells, cultured; acute lymphoblastic leukemia; cell lineage; transcription factors; dna; amino acid sequence; molecular sequence data; infant; reverse transcriptase polymerase chain reaction; base sequence; dna mutational analysis; conformational transition; zinc finger protein; protein determination; t cell leukemia; subcellular fractions; protein isoforms; ikaros transcription factor; zinc fingers; binding, competitive; leukemia, t-cell, acute; genes, dominant; humans; human; male; female; priority journal; article; cell compartmentation
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