RNA-binding protein quaking, a critical regulator of colon epithelial differentiation and a suppressor of colon cancer.
OBJECTIVE
Colon cancer is one of the best understood neoplasms from a genetic perspective, yet it remains the second most common cause of cancer-related death. Post-transcriptional regulation mediated by RNA-binding proteins or microRNAs coordinately targets multiple genes, holding promise involved in colon cancer initiation and development. Here we studied the role of RNA-binding protein quaking (QKI) in colon cancer.


METHODS
We observed the expression pattern of QKI in normal colon and colon cancers through reverse-transcription polymerase chain reaction and Western blot. Bisulfite sequencing and methylation-specific PCR were applied for QKI promoter methylation analysis. We used enterocyte differentiation markers and soft agar assay to test the role of QKI in colon differentiation and colon cancer development. 3' Untranslated region (UTR) reporter assay and RNA-immunoprecipitation were used to confirm the interaction between QKI and beta-catenin or p27.


RESULTS
QKI is significantly down-regulated and even absent in some colon cancers, which is at least partially because of the promoter hypermethylation. Forced expression of QKI in the colon cancer cells increased the expression of enterocyte differentiation marker intestinal alkaline phosphatase and lactase, together with the enhancement of p27Kip1 protein level, and membrane localized beta-catenin. Finally, QKI overexpression reduced the proliferation and tumorigenesis ability.


CONCLUSIONS
Our study establishes that QKI functions as a principal regulator in the differentiation of colon epithelium and a suppressor of carcinogenesis through coordinately targeting multiple genes associated with cell growth and differentiation, whose deregulation by methylation is involved in colon cancer onset and progress.
Yang
Guodong
G
The State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, the Fourth Military Medical University, Xi'an, China.
Fu
Haiyan
H
Zhang
Jie
J
Lu
Xiaozhao
X
Yu
Fang
F
Jin
Liang
L
Bai
Liyuan
L
Huang
Bo
B
Shen
Lan
L
Feng
Yue
Y
Yao
Libo
L
Lu
Zifan
Z
D000328:Adult; D000368:Aged; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D003110:Colonic Neoplasms / Q000235:genetics* / Q000473:pathology*; D019175:DNA Methylation / Q000502:physiology; D020895:Enterocytes / Q000166:cytology* / Q000502:physiology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000502:physiology; D008297:Male; D035683:MicroRNAs / Q000235:genetics; D008875:Middle Aged; D018809:Proliferating Cell Nuclear Antigen / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000502:physiology; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*
D035683:MicroRNAs; D018809:Proliferating Cell Nuclear Antigen; C490832:QKI protein, human; D016601:RNA-Binding Proteins; C413374:p27 antigen
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