The Flt3 internal tandem duplication mutant inhibits the function of transcriptional repressors by blocking interactions with SMRT.
Fms-like tyrosine kinase 3 (Flt3) is a type III receptor tyrosine kinase (RTK). Between 20% and 30% of acute myeloid leukemia (AML) patients have either an internal tandem duplication (ITD) of the juxtamembrane region or a point mutation of the Flt3 receptor leading to the constitutive activation of downstream signaling pathways and aberrant cell growth. The silencing mediator of retinoic and thyroid hormone receptors (SMRT) corepressor mediates transcriptional repression by interacting with transcription factors such as the promyelocytic leukemia zinc finger (PLZF) protein. Previous reports indicate that SMRT interaction with transcription factors can be disrupted by phosphorylation through activation of RTK pathways. We report here that the Flt3-ITD interferes with the transcriptional and biologic action of the PLZF transcriptional repressor. In the presence of Flt3-ITD, PLZF-SMRT interaction was reduced, transcriptional repression by PLZF was inhibited, and PLZF-mediated growth suppression of leukemia cells was partially blocked. Furthermore, overexpression of Flt3-ITD led to a partial relocalization of SMRT protein from the nucleus to the cytoplasm. Nuclear export was dependent on the SMRT receptor interaction domain (RID), and Flt3-ITD enhances the binding of nuclear-cytoplasm shuttling protein nuclear factor-kappaB-p65 (NFkappaB-p65) to this region. These data suggest that activating mutations of Flt3 may disrupt transcriptional repressor function resulting in aberrant gene regulation and abnormal leukemia cell growth.
Division of Hematology/Oncology, Department of Medicine, Mount Sinai School of Medicine, Box 1079, One Gustave Levy Place, New York, NY 10029, USA.
Shinichiro
S
Takahashi
Melanie J
MJ
McConnell
Hideo
H
Harigae
Mitsuo
M
Kaku
Takeshi
T
Sasaki
Ari M
AM
Melnick
Jonathan D
JD
Licht
D000818:Animals; D002455:Cell Division; D002460:Cell Line; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism*; D020440:Gene Duplication; D005786:Gene Expression Regulation / Q000235:genetics*; D020868:Gene Silencing; D006801:Humans; D051741:Kruppel-Like Transcription Factors; D007938:Leukemia; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D056985:Nuclear Receptor Co-Repressor 2; D000075722:Promyelocytic Leukemia Zinc Finger Protein; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*; D014162:Transfection
D004268:DNA-Binding Proteins; D051741:Kruppel-Like Transcription Factors; D008565:Membrane Proteins; C539130:NCOR2 protein, human; C539131:Ncor2 protein, mouse; D056985:Nuclear Receptor Co-Repressor 2; D000075722:Promyelocytic Leukemia Zinc Finger Protein; D011994:Recombinant Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C513267:Zbtb16 protein, mouse; C084881:flt3 ligand protein; C092037:ZBTB16 protein, human