A natural antisense transcript regulates Zeb2/Sip1 gene expression during Snail1-induced epithelial–mesenchymal transition

Abstract

Expression of Snail1 in epithelial cells triggers an epithelial-mesenchymal transition (EMT). Here, we demonstrate that the synthesis of Zeb2, a transcriptional repressor of E-cadherin, is up-regulated after Snail1-induced EMT. Snail1 does not affect the synthesis of Zeb2 mRNA, but prevents the processing of a large intron located in its 5-untranslated region (UTR). This intron contains an internal ribosome entry site (IRES) necessary for the expression of Zeb2. Maintenance of 5-UTR Zeb2 intron is dependent on the expression of a natural antisense transcript (NAT) that overlaps the 5 splice site in the intron. Ectopic overexpression of this NAT in epithelial cells prevents splicing of the Zeb2 5-UTR, increases the levels of Zeb2 protein, and consequently down-regulates E-cadherin mRNA and protein. The relevance of these results is demonstrated by the strong association between NAT presence and conservation of the 5-UTR intron in cells that have undergone EMT or in human tumors with low E-cadherin expression. Therefore, the results presented in this article reveal the existence of a NAT capable of activating Zeb2 expression, explain the mechanism involved in this activation, and demonstrate that this NAT regulates E-cadherin expression.

Phenotype and genotype of 87 patients with Mowat–Wilson syndrome and recommendations for care

“…These locus deletions often span several megabases of DNA and include other genes and long noncoding RNAs, such as the ZEB2-antisense transcripts encoded in the 5′ portion of ZEB2 and involved in its transcriptional regulation. 30 The variability and extent of these deletions may explain why they are usually associated with increased severity of some aspects, such as sitting age and onset of speech (Figure 3d). Full-gene deletion, or to a lesser extent the presence of a residual defective protein, also seems to negatively influence the number of cardiac defects, although their combined numbers are too small compared with cases of protein absence due to intragenic mutations (Figure 3e).…”

Transcriptional regulation of cell polarity in EMT and cancer

“…These different EMT regulators share a similar basic molecular mechanism of repression, binding to conserved E-box sequences (mainly of the CAGGTG type) in the proximal promoter of E-cadherin and other epithelial genes (Peinado et al, 2004(Peinado et al, , 2007. The mechanisms underlying the upregulation of mesenchymal motility or survival genes are still poorly understood, but they probably involve indirect activation pathways (Vega et al, 2004;Jorda`et al, 2005;Grotegut et al, 2006;Beltran et al, 2008).…”

“…Very recently, significant insights have been obtained into the modulation of ZEB factors expression, which implicated noncoding RNAs in new post-transcriptional mechanisms. ZEB1/ZEB2 expression is downregulated in epithelial cells through selective targeting of their mRNAs by several microRNAs (Gregory et al, 2008;Korpal et al, 2008;Park et al, 2008) or other non-coding RNAs (Beltran et al, 2008). MicroRNAs are short non-coding RNAs (20-22 nt long) that control gene expression at the post-transcriptional level by pairing their seed sequences (2-8 nt at the 5 0 -end) to complementary sequences located in the 3 0 -UTR region of target mRNAs (He and Hannon, 2004).…”

“…Although no studies have yet examined the effect of Twist on cell polarity genes, it is likely that they may also be downregulated during the EMT processes mediated by Twist. There is also evidence that Snai1 and ZEB2 can be upregulated by a distinct post-transcriptional mechanism (Beltran et al, 2008). In this case, SNAI1 mediates the induction of a natural antisense transcript of ZEB2 that prevents splicing of a 5 0 -UTR intron containing an internal ribosomal entry site, thereby favouring ZEB2 mRNA translation (Beltran et al, 2008) These observations, together with the potent repression of cell polarity genes by Snail and ZEB outlined above, support an active function of microRNAs or other non-coding RNAs in the regulation of apicalbasal polarity.…”

“…There is also evidence that Snai1 and ZEB2 can be upregulated by a distinct post-transcriptional mechanism (Beltran et al, 2008). In this case, SNAI1 mediates the induction of a natural antisense transcript of ZEB2 that prevents splicing of a 5 0 -UTR intron containing an internal ribosomal entry site, thereby favouring ZEB2 mRNA translation (Beltran et al, 2008) These observations, together with the potent repression of cell polarity genes by Snail and ZEB outlined above, support an active function of microRNAs or other non-coding RNAs in the regulation of apicalbasal polarity. It will therefore be important to analyse the relationship between the expression of non-coding RNAs, EMT inducers and core polarity genes in carcinoma cell lines and tumours.…”