title: miR-203 regulates cell proliferation through its influence on Hakai expression.
abstract: Gene expression is potently regulated through the action of microRNAs (miRNAs). Here, we present evidence of a miRNA regulating Hakai protein. Hakai was discovered as an E3 ubiquitin-ligase that mediates the posttranslational downregulation of E-cadherin, a major component of adherens junctions in epithelial cells and a potent tumour suppressor. Recent data have provided evidence that Hakai affects cell proliferation in an E-cadherin-independent manner, thus revealing a role for Hakai in the early stages of tumour progression. Furthermore, Hakai is highly up-regulated in human colon adenocarcinomas compared to normal tissues. However, the molecular mechanisms that regulate Hakai abundance are unknown. We identified two putative sites of miR-203 interaction on the Hakai mRNA, in its 3'-untranslated region (UTR). In several human carcinoma cell lines tested, overexpression of a miR-203 precursor (Pre-miR-203) reduced Hakai abundance, while inhibiting miR-203 by using an antisense RNA (Anti-miR-203) elevated Hakai levels. The repressive influence of miR-203 on the Hakai 3'-UTR was confirmed using heterologous reporter constructs. In keeping with Hakai's proliferative influence, Anti-miR-203 significantly increased cell number and BrdU incorporation, while Pre-miR-203 reduced these parameters. Importantly, the growth-promoting effects of anti-miR-203 required the presence of Hakai, because downregulation of Hakai by siRNA suppressed its proliferative action. Finally, in situ hybridization showed that miR-203 expression is attenuated in colon tumour tissues compared to normal colon tissues, suggesting that miR-203 could be a potential new prognostic marker and therapeutic target to explore in colon cancer. In conclusion, our findings reveal, for the first time, a post-transcriptional regulator of Hakai expression. Furthermore, by lowering Hakai abundance, miR-203 also reduces Hakai-regulated-cell division.
authors.affiliation: Translational Cancer Research Group, Instituto de Investigación Biomédica A Coruña (INIBIC), Complexo Hospitalario Universitario A Coruña (CHUAC)-SERGAS, A Coruña, Spain.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Abella
authors.forename: Manuel
authors.initials: M
authors.lastname: Valladares
authors.forename: Teresa
authors.initials: T
authors.lastname: Rodriguez
authors.forename: Mar
authors.initials: M
authors.lastname: Haz
authors.forename: Moisés
authors.initials: M
authors.lastname: Blanco
authors.forename: Nuria
authors.initials: N
authors.lastname: Tarrío
authors.forename: Pilar
authors.initials: P
authors.lastname: Iglesias
authors.forename: Luís A
authors.initials: LA
authors.lastname: Aparicio
authors.forename: Angélica
authors.initials: A
authors.lastname: Figueroa
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003106:Colon / Q000378:metabolism / Q000473:pathology; D003110:Colonic Neoplasms / Q000235:genetics / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism
chemical_list: C546703:MIRN203 microRNA, human; D035683:MicroRNAs; C471638:CBLL1 protein, human; D044767:Ubiquitin-Protein Ligases