Browsing by Author "Elias, Adriana"
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- Internal ribosome entry site-mediated translation of UPF1 contributes to its oncogenic role in colorectal cancerPublication . Lacerda, Rafaela; Menezes, Juliane; Elias, Adriana; Romão, LuísaColorectal cancer (CRC) is the third cause of death worldwide and projections point towards an increase for the next two decades. Many genes are misregulated in CRC, contributing to the development of the disease. Up-frameshift 1 (UPF1) is involved in many cellular mechanisms such as nonsense-mediated mRNA decay, cell cycle progression, or telomere maintenance and homeostasis. It also works as a tumour suppressor protein in most cancers but not in CRC, in which UPF1 plays an oncogenic role. We used the Xena platform to perform in silico analyses that revealed UPF1 is overexpressed in CRC contrary to several other analysed cancers. Besides, UPF1 expression levels are increased in CRC compared to the counterpart normal tissues. Experimentally, we confirmed these data and observed that endogenous UPF1 expression is maintained in different CRC cell lines under endoplasmic reticulum (ER) stress. To understand the mechanism underlying such maintenance, we used a bicistronic reporter construct to test whether UPF1 5’UTR can mediate alternative translation initiation and we concluded that such sequence contains an internal ribosome entry site (IRES) that maintains UPF1 expression in both normal and stress conditions in a 5’ cap-independent way. Deletional and mutational analysis of UPF1 5’UTR showed that nucleotides 1–100 (stem loop (SL) I) and 151–275 (SL III) — out of 275 nucleotides — are the minimal required sequences for the IRES to work properly. Using RNA antisense oligonucleotides (ASOs) targeting UPF1 IRES SL I and III, we observed a reduced UPF1 expression in HCT116 (CRC) cells. Altogether, these results suggest that UPF1 expression levels are maintained by the IRES-mediated translation mechanisms under conditions impairing canonical translation, such as those that mimic the tumour microenvironment. Thus, ASOs may be an upcoming therapy to target such alternative mechanism of translation initiation and prevent CRC development.
- The role of UPF1 cap-independent translation in colorectal cancerPublication . Lacerda, Rafaela; Menezes,Juliane; Elias, Adriana; Sousa, Sofia de; Romão, LuísaColorectal cancer (CRC) is one of the deadliest diseases worldwide with projections pointing towards an increase for the next two decades. Translation dysregulation of many genes contributes to CRC development, and here we are studying the role of translation dysregulation of up-frameshift 1 (UPF1) in CRC. This protein is involved in many cellular mechanisms such as nonsense-mediated mRNA decay, cell cycle progression, or telomere maintenance and homeostasis. It also works as a tumour suppressor protein in most cancers but not in CRC, in which UPF1 plays an oncogenic role. We used the Xena platform to perform in silico analyses that revealed UPF1 protein overexpressed in CRC, contrary to several other analysed cancers. Besides, UPF1 protein levels are increased in CRC compared to the counterpart normal tissues. Experimentally, we confirmed that UPF1 protein expression is maintained in different CRC cell lines under normal conditions or endoplasmic reticulum (ER) stress. To understand the mechanism underlying such maintenance, we used a bicistronic reporter construct to test whether UPF1 5’ untranslated region (UTR) can mediate alternative translation initiation and we concluded that such sequence drives cap-independent translation initiation, in both normal and stress conditions. Deletional and mutational analyses of UPF1 5’UTR showed that nucleotides 1–100 [stem-loop (SL) I] and 151–275 (SL III) — out of 275 nucleotides — are the minimal required sequences for the cap-independent translation initiation mechanism to work properly. Using RNA antisense oligonucleotides (ASOs) targeting UPF1 SL I and III, we observed a reduced UPF1 expression in HCT116 (CRC) cells, supporting the functional role of SL I and SL III in mediating cap-independent translation. Altogether, these results highlight the importance of cap-independent translation initiation in UPF1 expression regulation, in conditions that mimic the tumour microenvironment, and this might be used as a therapeutic target.