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.
Han
Weidong
W
Department of Molecular Biology, Chinese PLA General Hospital, Beijing 100853, China. hanwdrsw69@yahoo.com
Wu
Zhiqiang
Z
Zhao
Yali
Y
Meng
Yuanguang
Y
Si
Yiling
Y
Yang
Jie
J
Fu
Xiaobing
X
Yu
Li
L
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