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Vol. 18, Issue 12, 5004-5013, December 2007

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Epidermal Growth Factor Increases the Interaction between Nucleolin and Heterogeneous Nuclear Ribonucleoprotein K/Poly(C) Binding Protein 1 Complex to Regulate the Gastrin mRNA Turnover

Pin-Tse Lee^*,, Pao-Chi Liao, Wen-Chang Chang^*,, and Joseph T. Tseng^*

*Department of Pharmacology and Institute of Basic Medical Sciences, College of Medicine, and Center for Gene Regulation and Signal Transduction Research, National Cheng Kung University, Tainan, Taiwan 701; and Department of Occupational Health, College of Medicine, National Cheng Kung University, Tainan, Taiwan 701

Submitted April 27, 2007; Revised September 21, 2007; Accepted October 3, 2007
Monitoring Editor: William Tansey

Gastrin, a gastrointestinal hormone responsible for gastric acid secretion, has been confirmed as a growth factor for gastrointestinal tract malignancies. High expression of gastrin mRNA was observed in pancreatic and colorectal cancer; however, the mechanism is unclear. Epidermal growth factor (EGF) was found to increase gastrin mRNA stability, indicating mRNA turnover regulation mechanism is involved in the control of gastrin mRNA expression. Using biotin-labeled RNA probe pull-down assay combined with mass spectrometry analysis, we identified the heterogeneous nuclear ribonucleoprotein K (hnRNP K) and poly(C) binding protein 1 (PCBP1) bound with the C-rich region in gastrin mRNA 3' untranslated region. Nucleolin bound with the AGCCCU motif and interacted with hnRNP K were also demonstrated. Under EGF treatment, we observed the amount of nucleolin interacting with hnRNP K and gastrin mRNA increased. Using small interfering RNA technology to define their functional roles, we found hnRNP K, PCBP1, and nucleolin were all responsible for stabilizing gastrin mRNA. Moreover, nucleolin plays a crucial role in mediating the increased gastrin mRNA stability induced by EGF signaling. Besides, we also observed hnRNP K/PCBP1 complex bound with the C-rich region in the gastrin mRNA increased nucleolin binding with gastrin mRNA. Finally, a novel binding model was proposed.

Address correspondence to: Joseph T. Tseng (tctseng{at}mail.ncku.edu.tw) or Wen-Chang Chang (wcchang{at}mail.ncku.edu.tw).

Abbreviations used: 3'UTR, 3' untranslated region; EGF, epidermal growth factor; hnRNP K, heterogeneous nuclear ribonucleoprotein K; PCBP1, poly(C) binding protein 1.