MEF2C is activated by multiple mechanisms in a subset of T-acute lymphoblastic leukemia cell lines.
In T-cell acute lymphoblastic leukemia (T-ALL) the cardiac homeobox gene NKX2-5 (at 5q35) is variously deregulated by regulatory elements coordinating with BCL11B (at 14q32.2), or the T-cell receptor gene TRD (at 14q11.2), respectively. NKX2-5 is normally expressed in developing spleen and heart, regulating fundamental processes, including differentiation and survival. In this study we investigated whether NKX2-5 expression in T-ALL cell lines reactivates these embryonal pathways contributing to leukemogenesis. Among 18 known targets analyzed, we identified three genes regulated by NKX2-5 in T-ALL cells, including myocyte enhancer factor 2C (MEF2C). Knockdown and overexpression assays confirmed MEF2C activation by NKX2-5 at both the RNA and protein levels. Direct interactions between NKX2-5 and GATA3 as indicated by co-immunoprecipitation data may contribute to MEF2C regulation. In T-ALL cell lines LOUCY and RPMI-8402 MEF2C expression was correlated with a 5q14 deletion, encompassing noncoding proximal gene regions. Fusion constructs with green fluorescent protein permitted subcellular detection of MEF2C protein in nuclear speckles interpretable as repression complexes. MEF2C consistently inhibits expression of NR4A1/NUR77, which regulates apoptosis via BCL2 transformation. Taken together, our data identify distinct mechanisms underlying ectopic MEF2C expression in T-ALL, either as a downstream target of NKX2-5, or via chromosomal aberrations deleting proximal gene regions.
Nagel
S
S
Human and Animal Cell Cultures, DSMZ, Braunschweig, Germany. sna@dsmz.de
Meyer
C
C
Quentmeier
H
H
Kaufmann
M
M
Drexler
H G
HG
MacLeod
R A F
RA
D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism; D002872:Chromosome Deletion; D002895:Chromosomes, Human, Pair 5 / Q000235:genetics / Q000648:ultrastructure; D004268:DNA-Binding Proteins / Q000032:analysis / Q000502:physiology*; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D015973:Gene Expression Regulation, Leukemic; D020868:Gene Silencing; D005801:Genes, Homeobox; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D006801:Humans; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D026161:MADS Domain Proteins / Q000502:physiology*; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors / Q000502:physiology*; D009363:Neoplasm Proteins / Q000502:physiology*; D056985:Nuclear Receptor Co-Repressor 2; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D011987:Receptors, Steroid / Q000502:physiology*; D012097:Repressor Proteins / Q000032:analysis; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*
D004268:DNA-Binding Proteins; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; C578040:MEF2C protein, human; D018006:Myogenic Regulatory Factors; C539130:NCOR2 protein, human; C095552:NKX2-5 protein, human; C539821:NR4A1 protein, human; D009363:Neoplasm Proteins; D056985:Nuclear Receptor Co-Repressor 2; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D012097:Repressor Proteins; D014157:Transcription Factors