ID signaling (Homo sapiens)

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The Inhibitor of DNA binding (ID) proteins belong to the class V HLH family of transcription factors. Four ID proteins (ID 1-4)

 are known in humans. Unlike the basic HLH (bHLH) transcription factors, ID proteins lack the basic DNA binding region. They can heterodimerize with class I bHLH 
 transcription factors to form inactive complexes. They thus act as dominant negative inhibitors of the class I bHLH transcription factors. They are also capable of 
 regulating the activity of class II HLH transcription factors. Since, class I and II HLH proteins regulate the expression of cell type-specific genes and differentiated 
 phenotype, ID proteins are thought to regulate the cross-talk between the pathways involved in cell growth and differentiation. Aberrant expression of ID proteins are 
 found in many primary tumors and are found to regulate many steps in cancer progression including neo-angiogenesis, invasion and migration, proliferation and growth, 
 cell-cell interaction and differentiation. These include head and neck squamous cell carcinoma, esophageal squamous cell carcinoma, melanoma, hepatocellular carcinonoma, 
 pancreatic cancer, ovarian cancer, cervical cancer, breast cancer  and prostate cancer. Among the transcription factors that ID proteins associate with are the Ets family 
 members (ELKs)  and paired box family (PAXs). They can also bind to the retinoblastoma and retinoblastoma-like proteins (RBLs), which are thought to be tumor suppressors. 
 IDs can also be phosphorylated by CDK2.
 

NetPath_16 -ID signaling pathway. NetPath (http://www.netpath.org) is a collaborative project between PandeyLab at Johns Hopkins University (http://pandeylab.igm.jhmi.edu) and the Institute of Bioinformatics (http://www.ibioinformatics.org). If you use this pathway, you must cite the NetPath website until the pathway is published.