Intrinsically disordered human C/EBP homologous protein regulates biological activity of colon cancer cells during calcium stress.
Intrinsically disordered proteins are emerging as substantial functional constituents of mammalian proteomes. Although the abundance of these proteins has been established by bioinformatics approaches, the vast majority have not been characterized structurally or functionally. The C/EBP homologous protein (CHOP) is a proto-oncogene, traditionally shown as a dominant-negative inhibitor of C/EBPs and a transcriptional activator of activating protein-1. We report here the in vitro characterization of CHOP, where our computational analyses and experimental evidences show for the first time that CHOP is an intrinsically disordered protein. Intrinsic fluorescence, NMR spectroscopy, and analytical size-exclusion chromatography studies indicate that CHOP contains extensive disordered regions and self-associate in solution. Interestingly, the disordered N-terminal region has a key role in the oligomerization of CHOP and is vital for its biological activity. We report a novel mechanistic role of CHOP in the inhibition of Wnt/TCF signaling and stimulation of c-Jun and sucrase-isomaltase reporter activity in intestinal colon cancer cells. These findings are discussed in the context of oligomerization of intrinsically disordered proteins as one of the mechanisms through which they exert their biological function.
Singh
Vinay K
VK
Department of Biochemistry, Queen's University, Kingston, Ontario, Canada.
Pacheco
Ivan
I
Uversky
Vladimir N
VN
Smith
Steven P
SP
MacLeod
R John
RJ
Jia
Zongchao
Z
D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D017930:Genes, Reporter; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D000090063:Proto-Oncogene Mas; D034622:RNA Interference; D044169:Receptors, Calcium-Sensing / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013394:Sucrase-Isomaltase Complex / Q000235:genetics / Q000378:metabolism; D051742:Transcription Factor CHOP / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
C095550:CASR protein, human; D022762:CCAAT-Enhancer-Binding Proteins; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D044169:Receptors, Calcium-Sensing; D011993:Recombinant Fusion Proteins; D051176:beta Catenin; D051742:Transcription Factor CHOP; D048031:JNK Mitogen-Activated Protein Kinases; D013394:Sucrase-Isomaltase Complex; D002118:Calcium