Loss of Scribble Promotes Snail Translation through Translocation of HuR and Enhances Cancer Drug Resistance.
Bottom Line: Furthermore, we demonstrate HuR can recognize AU-rich elements of the Snail-encoding mRNA, thereby regulating Snail translation.Moreover, loss of Scribble-induced HuR translocation mediates the accumulation of Snail via activation of the p38 MAPK pathway.Thus, this work clarifies the role of polarity protein Scribble, which is directly implicated in the regulation of developmental transcription factor Snail, and suggesting a mechanism for Scribble mediating cancer drug resistance.
Affiliation: From the Key Laboratory of Nutrition and Metabolism, Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, China.Show MeSH
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Mentions: To analyze the molecular mechanism of the effect of Scribble on Snail accumulation, we examined Snail mRNA levels and Snail mRNA stability upon exposure to the transcription inhibitor actinomycin D. Neither the level nor stability of the transcript were significantly changed in response to Scribble KD compared with control cells (Fig. 3, A and B), suggesting that Scribble may regulate Snail accumulation at a post-transcriptional level. Following administration of MG132 at various time points, the rate of Snail protein synthesis was higher in Scribble KD cells while compared with control cells (Fig. 3C). The results from the time course of treatment in Scribble KD cells with cycloheximide, a protein synthesis inhibitor, indicated no apparent changes in the degradation or the half-life of Snail protein (Fig. 3D). We therefore supposed that Scribble regulates Snail accumulation at the level of translation. To further substantiate this impact of Scribble KD on Snail translation, we performed polyribosome profiling of cytoplasmic lysates from Scribble KD and control cells. In control cells, ∼25% of Snail mRNA co-sedimented with unbound ribonucleoprotein particles (RNPs) and mono-bound RNPs, and the remaining ∼75% of Snail mRNA co-sedimented with polyribosomes. In KD Scribble cells, approximately ∼90% of Snail mRNA co-sedimented with polyribosomes (Fig. 3E). These results indicated that the KD of Scribble increased the proportion of Snail mRNA in polyribosome fractions, yielding increased translation of Snail transcript.
Affiliation: From the Key Laboratory of Nutrition and Metabolism, Key Laboratory of Food Safety Research, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, China.