Percorrer por autor "Costa, Paulo J. da"
A mostrar 1 - 4 de 4
Resultados por página
Opções de ordenação
- Functional networks of DIS3L2 in cancer and NMDPublication . Garcia-Moreno, Juan; Costa, Paulo J. da; Gama-Carvalho, Margarida; Matos, Paulo; Romão, LuísaIn the flow of information from DNA to mRNA to proteins, mRNAs undergo a number of processing steps, since they are synthesized in the nucleus, until they are translated in the cytoplasm. Eukaryotic cells tightly control the fidelity of this process, via quality control pathways, among them, the nonsense-mediated mRNA decay (NMD). NMD recognizes and degrades mRNAs harboring premature translation-termination codons (PTCs) and regulates normal and fully functional mRNA levels. A new branch of the NMD pathway is starting to be revealed, which is characterized by the involvement of the DIS3L2 3’ to 5’ exoribonuclease. This protein has special relevance, given its exosome-independent action and its uridylation-mediated decay. Interestingly, mutations on this ribonuclease induce deregulation of cell-cycle genes leading to a faster cell growth and decreased chromosome stability. In this project, we aim to analyze how DIS3L2 and uridylation regulate the human transcriptome, in order to shed light on how this ribonuclease is related to NMD and how its deregulation contributes to tumorigenesis. For this purpose, high-throughput mRNA sequencing has been performed in the SW480 colorectal cancer cell line depleted of DIS3L2 or DIS3L2 plus terminal uridylyl transferases (TUTases), TUT4 and TUT7. Gene ontology analysis over the set of genes up-regulated under those two conditions, show enrichment in molecular functions and biological processes related with cancer, and cell events directly implicated RNA processing and RNA degradation. Preliminary results on genetic features in the pool of deregulated transcripts also show significant differences between conditions, an important aspect that will guide us to determine grades of sensitivities in the decay of DIS3L2-subtrates. Currently, we are setting various approaches in order to unveil the role of DIS3L2 in oncogenesis and go deeper in its substrate preference.
- Mechanistic aspects of nonsense-mediated mRNA decay in human cellsPublication . Costa, Paulo J. da; Menezes, Juliane; Saramago, Margarida; García-Moreno, Juan F.; Santos, Hugo A.; Gama-Carvalho, Margarida; Arraiano, Cecília M.; Viegas, Sandra C; Romão, LuísaThe nonsense-mediated mRNA decay (NMD) pathway selectively degrades mRNAs carrying a premature translation-termination codon but also regulates the abundance of a large number of physiological RNAs that encode full-length proteins. NMD results from improper translation termination at stop codons, and thus, it is a cytoplasmic and translation-dependent process. In human cells, mRNA decay inherent to NMD involves an endonucleolytic cleavage near the stop codon and exonucleolytic degradation from both 5’ and 3’ ends. This is done by a process not yet completely understood that recruits decapping and 5’-to-3’ exonuclease activities, as well as deadenylating and 3’-to-5’ exonuclease exosome activities. In yeast, DIS3/Rrp44 protein is the catalytic subunit of the exosome, but in humans, there are three known paralogues of this enzyme: DIS3, DIS3L1, and DIS3L2. However, DIS3L2 exoribonuclease activity is independent of the exosome. DIS3L1 and DIS3L2 exoribonucleases localize in the same compartment where NMD occurs, however little is known about their role in this process. In order to unveil the role of DIS3L2 in NMD, we performed its knockdown in HeLa cells and measured the mRNA levels of various natural NMD-targets. Our results show that some NMD-targets accumulate in DIS3L2-depleted cells. In addition, mRNA half-life analysis indicated that these NMD-targets are direct DIS3L2 substrates. Besides, we observed that DIS3L2 acts over full-length transcripts, being DIS3L2-mediated decay dependent on the activity of the terminal uridylyl transferases (TUTases) Zcchc6/11 (TUT7/4). Together, our findings establish the role of DIS3L2 and uridylation over human NMD-targets.
- A role for DIS3L2 over natural nonsense-mediated mRNA decay targets in human cellsPublication . Costa, Paulo J. da; Menezes, Juliane; Saramago, Margarida; García-Moreno, Juan F.; Santos, Hugo A.; Gama-Carvalho, Margarida; Arraiano, Cecília M.; Romão, LuísaThe nonsense-mediated decay (NMD) pathway selectively degrades mRNAs carrying a premature translation-termination codon but also regulates the abundance of a large number of physiological mRNAs that encode full-length proteins. In human cells, NMD-targeted mRNAs are degraded by endonucleolytic cleavage and exonucleolytic degradation from both 5-' and 3'-ends. This is done by a process not yet completely understood that recruits decapping and 5'-to-3' exonuclease activities, as well as deadenylating and 3'-to-5' exonuclease exosome activities. In yeast, DIS3/Rrp44 protein is the catalytic subunit of the exosome, but in humans, there are three known paralogues of this enzyme: DIS3, DIS3L1, and DIS3L2. However, little is known about their role in NMD. Here, we show that some NMD-targets are DIS3L2 substrates in human cells. In addition, we observed that DIS3L2 acts over full-length transcripts, through a process that also involves UPF1. Moreover, DIS3L2-mediated decay is dependent on the activity of the terminal uridylyl transferases Zcchc6/11 (TUT7/4). Together, our findings establish a role for DIS3L2 and uridylation in NMD.
- Transcriptomic screen for DIS3, DIS3L1 and DIS3L2-associated functional networks in colorectal cancerPublication . Costa, Paulo J. da; Saramago, Margarida; Viegas, Sandra C.; Arraiano, Cecília; Santos, Hugo; Gama-Carvalho, Margarida; Romão, LuísaThe final step of eukaryotic mRNA degradation proceeds in either a 5’-3’ direction, catalyzed by XRN1, or in a 3’-5’ direction catalyzed by DIS3, DIS3L1 (the catalytic subunits of the exosome) and/or DIS3L2 (exosome-independent). Important findings over the last years have shed a new light onto the mechanistic details of RNA degradation by these exoribonucleases. In addition, it has been shown that they are involved in growth, mitotic control and important human diseases, including cancer. In this work, we aim to analyze how DIS3, DIS3L1 and DIS3L2 regulate the human transcriptome, and how their functional interactions modulate the transcriptional reprogramming of colorectal cancer cells. Each one of these nucleases was depleted by RNA interference in HeLa cells and levels of several endogenous targets was monitored by RT-qPCR. Our results show that these exoribonucleases are target specific and not directly involved in any known mRNA decay mechanisms such as nonsense-mediated decay (NMD). However, we do not know yet what defines such target preference. In parallel, our bioinformatics analysis of available transcriptomic data from cells depleted of DIS3L1, DIS3L2, XRN1 or UPF1 (which has a central role in NMD) has shown some, but not full, redundancy among the transcripts regulated by these nucleases, which supports our experimental data. Presently, we are exploring the mechanism through which DIS3L2 is involved in NMD and how it modulates the expression of NMD targets.