Table 2.

Protein-protein interactions involving Id proteins

Id protein	Protein partner	Description	References
Id1-4	Class I and II bHLH proteins	Dominant negative regulation of bHLH factors	[61–63, 236]
Id2	pRb and related pocket proteins p107 and p130	Inhibition of pRb-mediated cell-cycle arrest (as no interaction between the pRb small pocket and Id2 was detected by mass spectrometry and NMR spectroscopy [136], a multiprotein complex is likely to be formed)	[64, 65]
Id2	ENH	Id-protein localization in the cytoplasm by association of the Id2 HLH and ENH LIM domains	[66, 67]
Id1-3	p204	Id-protein localization in the cytoplasm	[68, 69]
Id1-3	Ets-domain proteins Elk-1 and SAP-1/-2	Inhibition of the winged-helix-turn-helix transcription factors regulating the expression of immediate-early response genes such as c-Fos and Egr1	[70]
Id1	MIDA1	Inhibition of MIDA1-Z-DNA interaction with stimulation of cell growth and inhibition of neural differentiation	[71, 72, 344, 345]
Id1-3	Pax-2/-5/-8	Inhibition of the paired-box transcription factors involved in development	[73]
Id1, Id2	Adenovirus E1A protein	Induction of apoptosis in cells expressing p53 mutants	[74]
Id2, Id3	ADD1/SREBP-1c	Inhibition of the bHLH-LZ transcription factor that regulates the expression of adipocyte genes	[75]
Id1	C8, HBX	Induction of proteasome-mediated HBX degradation	[76]
Id1	S5a	Suppression of the Id-protein activity	[77]
Id1, Id3	CSN5 (Id1, Id3), CSN7 (Id3)	Suppression of Id-protein ubiquitination by CSN-mediated phosphorylation	[78]
Id1-3	USP1	Id-protein deubiquitination	[79]
Id2	Apc/C subunits Apc1, Apc5, Apc8/Cdc23	Id2-protein degradation	[50]
Id1	Caveolin-1	Induction of cell migration and chemotherapy resistance in prostate cancer	[80]
Id1-4	FHL2	Antagonism of the inhibitory effect of the Id proteins on E47-mediated transcription	[81]
Id2	VHL-elongin-C	Inhibition of ubiquitination and degradation of HIF2α	[82]
Id1	ERβ1	Inhibition of cell proliferation and p21 up-regulation	[83]