FHL2 interacts with and acts as a functional repressor of Id2 in human neuroblastoma cells.
Inhibitor of differentiation 2 (Id2) is a natural inhibitor of the basic helix-loop-helix transcription factors. Although Id2 is well known to prevent differentiation and promote cell-cycle progression and tumorigenesis, the molecular events that regulate Id2 activity remain to be investigated. Here, we identified that Four-and-a-half LIM-only protein 2 (FHL2) is a novel functional repressor of Id2. Moreover, we demonstrated that FHL2 can directly interact with all members of the Id family (Id1-4) via an N-terminal loop-helix structure conserved in Id proteins. FHL2 antagonizes the inhibitory effect of Id proteins on basic helix-loop-helix protein E47-mediated transcription, which was abrogated by the deletion mutation of Ids that disrupted their interaction with FHL2. We also showed a competitive nature between FHL2 and E47 for binding Id2, whereby FHL2 prevents the formation of the Id2-E47 heterodimer, thus releasing E47 to DNA and restoring its transcriptional activity. FHL2 expression was remarkably up-regulated during retinoic acid-induced differentiation of neuroblastoma cells, during which the expression of Id2 was opposite to that. Ectopic FHL2 expression in neuroblastoma cells markedly reduces the transcriptional and cell-cycle promoting functions of Id2. Altogether, these results indicate that FHL2 is an important repressor of the oncogenic activity of Id2 in neuroblastoma cells.
Department of Molecular Biology, Chinese PLA General Hospital, Beijing 100853, China. hanwdrsw69@yahoo.com
Weidong
W
Han
Zhiqiang
Z
Wu
Yali
Y
Zhao
Yuanguang
Y
Meng
Yiling
Y
Si
Jie
J
Yang
Xiaobing
X
Fu
Li
L
Yu
D000818:Animals; D002453:Cell Cycle; D002454:Cell Differentiation; D002460:Cell Line; D045744:Cell Line, Tumor; D004247:DNA / Q000378:metabolism; D024721:E-Box Elements; D015972:Gene Expression Regulation, Neoplastic; D018257:Helix-Loop-Helix Motifs; D018398:Homeodomain Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D051797:Inhibitor of Differentiation Protein 2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D060850:LIM-Homeodomain Proteins; D009124:Muscle Proteins / Q000737:chemistry / Q000378:metabolism*; D009447:Neuroblastoma / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D051820:TCF Transcription Factors / Q000378:metabolism; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D015854:Up-Regulation
C105987:FHL2 protein, human; D018398:Homeodomain Proteins; C497450:ID2 protein, human; D051797:Inhibitor of Differentiation Protein 2; D060850:LIM-Homeodomain Proteins; D009124:Muscle Proteins; D012097:Repressor Proteins; D051820:TCF Transcription Factors; C544912:TCF7L1 protein, human; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors; D004247:DNA