Oncotarget

Priority Research Papers:

p73 expression is regulated by ribosomal protein RPL26 through mRNA translation and protein stability

Min Zhang, Jin Zhang, Wensheng Yan and Xinbin Chen _

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Oncotarget. 2016; 7:78255-78268. https://doi.org/10.18632/oncotarget.13126

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Abstract

Min Zhang1,2,*, Jin Zhang2,*, Wensheng Yan2 and Xinbin Chen2

1 College of Life Sciences and Technology, Huazhong Agricultural University, Wuhan, China

2 Comparative Oncology Laboratory, Schools of Veterinary Medicine and Medicine, University of California at Davis, Davis, CA, USA

* These authors have contributted equally to this work

Correspondence to:

Xinbin Chen, email:

Min Zhang, email:

Keywords: RPL26, p73, MDM2, eIF4E, protein stability

Received: April 01, 2016 Accepted: October 15, 2016 Published: November 04, 2016

Abstract

p73, a p53 family tumor suppressor, is regulated by multiple mechanisms, including transcription and mRNA and protein stability. However, whether p73 expression is regulated via mRNA translation has not been explored. To test this, we examined whether ribosomal protein 26 (RPL26) plays a role in p73 expression. Here, we showed that p73 expression is controlled by RPL26 via protein stability and mRNA translation. To examine whether MDM2 mediates RPL26 to regulate p73 protein stability, we generated multiple MDM2-knockout cell lines by CRISPR-cas9. We found that in the absence of MDM2, the half-life of p73 protein is markedly increased. Interestingly, we also found that RPL26 is still capable of regulating p73 expression, albeit to a lesser extent, in MDM2-KO cells compared to that in isogenic control cells, suggesting that RPL26 regulates p73 expression via multiple mechanisms. Indeed, we found that RPL26 is necessary for efficient assembly of polysomes on p73 mRNA and de novo synthesis of p73 protein. Consistently, we found that RPL26 directly binds to p73 3’ untranslated region (3’UTR) and that RPL26 is necessary for efficient expression of an eGFP reporter that carries p73 3′UTR. We also found that RPL26 interacts with cap-binding protein eIF4E and enhances the association of eIF4E with p73 mRNA, leading to increased p73 mRNA translation. Finally, we showed that knockdown of RPL26 promotes, whereas ectopic expression of RPL26 inhibits, cell growth in a TAp73-dependent manner. Together, our data indicate that RPL26 regulates p73 expression via two distinct mechanisms: protein stability and mRNA translation.


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