Lacerda, RafaelaMenezes, JulianeAntunes Elias, AdrianaRomão, Luísa2024-01-222023-11-23http://hdl.handle.net/10400.18/8936Colorectal cancer (CRC) is the third leading cause worldwide and projections point towards an increase over the next two decades. Gene expression dysregulation of several genes involved in CRC contribute to disease development. The up-frameshift 1 (UPF1) protein plays important roles in several cellular mechanisms and acts as a tumour suppressor in most cancers. However, in CRC, this protein has been described as working as an oncogenic protein. In order to understand the molecular mechanisms underlying the oncogenic role of UPF1 in CRC, we have analysed mRNA and protein levels in different types of cancer. In silico analyses have shown that UPF1 is overexpressed in CRC and lung cancer compared to the other analysed cancers. Also, UPF1 expression is significantly greater in CRC than in normal tissues. Experimentally, we observed that UPF1 expression is maintained under stress conditions that compromise global protein synthesis. In this regard, we tested whether UPF1 translation initiation can be mediated through an alternative cap-independent mechanism. We showed that the 5’ untranslated region (UTR) of UPF1 transcript allows cap-independent translation initiation and mapped the minimal sequence required for this mechanism to work. This region also mediates translation initiation in transcripts lacking a cap structure and under stress conditions like endoplasmic reticulum stress, hypoxia and mTOR pathway inhibition. Then, we designed antisense RNA oligonucleotides (ASOs) that target the minimal region and observed a reduced expression of UPF1 in CRC cells treated with those ASOs compared to cells treated with control ASOs. All in all, these results show that alternative translation initiation mediated through UPF1 5’UTR allows UPF1 expression levels to be maintained under conditions observed in the tumour microenvironment, which globally repress protein synthesis. Thus, ASOs targeting the minimal region responsible for allowing UPF1 expression can be the beginning of a new RNA-based therapy to prevent CRC development.engColorectal CancerUp-frameshift 1 (UPF1)Genómica FuncionalExpressão GénicaGenómica Funcional e Estruturalconference object