Expression of dominant-negative Ikaros isoforms in T-cell acute lymphoblastic leukemia.
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.
Sun
L
L
Parker Hughes Cancer Center and Children's Cancer Group ALL Biology Reference Laboratory, Hughes Institute, St. Paul, Minnesota 55113, USA.
Crotty
M L
ML
Sensel
M
M
Sather
H
H
Navara
C
C
Nachman
J
J
Steinherz
P G
PG
Gaynon
P S
PS
Seibel
N
N
Mao
C
C
Vassilev
A
A
Reaman
G H
GH
Uckun
F M
FM
D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D001667:Binding, Competitive / Q000235:genetics; D002451:Cell Compartmentation; D019070:Cell Lineage / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D004247:DNA / Q000378:metabolism; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins; D005260:Female; D005799:Genes, Dominant; D006801:Humans; D051740:Ikaros Transcription Factor; D007223:Infant; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D020033:Protein Isoforms / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013347:Subcellular Fractions / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D014407:Tumor Cells, Cultured; D016335:Zinc Fingers / Q000235:genetics
D004268:DNA-Binding Proteins; C497239:IKZF1 protein, human; D020033:Protein Isoforms; D014157:Transcription Factors; D051740:Ikaros Transcription Factor; D004247:DNA