RESUMO
Circular RNAs (circRNAs) are covalently closed RNA molecules widely expressed in eukaryotes and deregulated in several pathologies, including cancer. Many studies point to their activity as microRNAs (miRNAs) and protein sponges; however, we propose a function based on circRNA-mRNA interaction to regulate mRNA fate. We show that the widely tumor-associated circHIPK3 directly interacts in vivo with the BRCA1 mRNA through the back-splicing region in human cancer cells. This interaction increases BRCA1 translation by competing for the binding of the fragile-X mental retardation 1 protein (FMRP) protein, which we identified as a BRCA1 translational repressor. CircHIPK3 depletion or disruption of the circRNA-mRNA interaction decreases BRCA1 protein levels and increases DNA damage, sensitizing several cancer cells to DNA-damage-inducing agents and rendering them susceptible to synthetic lethality. Additionally, blocking FMRP interaction with BRCA1 mRNA with locked nucleic acid (LNA) restores physiological protein levels in BRCA1 hemizygous breast cancer cells, underscoring the importance of this circRNA-mRNA interaction in regulating DNA-damage response.
RESUMO
Circular RNAs (circRNAs) are widely expressed in eukaryotes and are regulated in many biological processes. Although several studies indicate their activity as microRNA (miRNA) and protein sponges, little is known about their ability to directly control mRNA homeostasis. We show that the widely expressed circZNF609 directly interacts with several mRNAs and increases their stability and/or translation by favoring the recruitment of the RNA-binding protein ELAVL1. Particularly, the interaction with CKAP5 mRNA, which interestingly overlaps the back-splicing junction, enhances CKAP5 translation, regulating microtubule function in cancer cells and sustaining cell-cycle progression. Finally, we show that circZNF609 downregulation increases the sensitivity of several cancer cell lines to different microtubule-targeting chemotherapeutic drugs and that locked nucleic acid (LNA) protectors against the pairing region on circZNF609 phenocopy such effects. These data set an example of how the small effects tuned by circZNF609/CKAP5 mRNA interaction might have a potent output in tumor growth and drug response.
Assuntos
Carcinogênese , Proteínas Associadas aos Microtúbulos/metabolismo , Microtúbulos/metabolismo , Neoplasias/metabolismo , RNA Circular/metabolismo , RNA Mensageiro/metabolismo , Animais , Antineoplásicos/farmacologia , Proteína Semelhante a ELAV 1/genética , Proteína Semelhante a ELAV 1/metabolismo , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Células K562 , Masculino , Camundongos Nus , Proteínas Associadas aos Microtúbulos/genética , Microtúbulos/efeitos dos fármacos , Microtúbulos/genética , Microtúbulos/patologia , Neoplasias/tratamento farmacológico , Neoplasias/genética , Neoplasias/patologia , RNA Circular/genética , RNA Mensageiro/genética , Transdução de Sinais , Carga Tumoral , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Circular RNAs (circRNAs), covalently closed RNAs that originate from back-splicing events, participate in the control of several processes, including those that occur in the development of pathological conditions such as cancer. Hereby, we describe circAFF1, a circular RNA overexpressed in alveolar rhabdomyosarcoma. Using RH4 and RH30 cell lines, a classical cell line models for alveolar rhabdomyosarcoma, we demonstrated that circAFF1 is a cytoplasmatic circRNA and its depletion impacts cell homeostasis favouring cell migration through the downregulation of genes involved in cell adhesion pathways. The presented data underline the importance of this circular RNA as a new partial suppressor of the alveolar rhabdomyosarcoma tumour progression and as a putative future therapeutic target.