Browsing by Author "Carvajal, Felipe"

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    Functional and Structural Analysis of the Internal Ribosome Entry Site Present in the mRNA of Natural Variants of the HIV-1
    (PUBLIC LIBRARY SCIENCE, 2012) Vallejos, Maricarmen; Carvajal, Felipe; Pino, Karla; Navarrete, Camilo; Ferres, Marcela; Pablo Huidobro Toro, Juan; Sargueil, Bruno; Lopez Lastra, Marcelo
    The 5'untranslated regions (UTR) of the full length mRNA of the HIV-1 proviral clones pNL4.3 and pLAI, harbor an internal ribosomal entry site (IRES). In this study we extend this finding by demonstrating that the mRNA 5'UTRs of natural variants of HIV-1 also exhibit IRES-activity. Cap-independent translational activity was demonstrated using bicistronic mRNAs in HeLa cells and in Xenopus laevis oocytes. The possibility that expression of the downstream cistron in these constructs was due to alternative splicing or to cryptic promoter activity was ruled out. The HIV-1 variants exhibited significant 5'UTR nucleotide diversity with respect to the control sequence recovered from pNL4.3. Interestingly, translational activity from the 5'UTR of some of the HIV-1 variants was enhanced relative to that observed for the 5'UTR of pNL4.3. In an attempt to explain these findings we probed the secondary structure of the variant HIV-1 5'UTRs using enzymatic and chemical approaches. Yet subsequent structural analyses did not reveal significant variations when compared to the pNL4.3-5'UTR. Thus, the increased IRES-activity observed for some of the HIV-1 variants cannot be ascribed to a specific structural modification. A model to explain these findings is proposed.
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    Oxygenation by Intravascular Photosynthesis Reduces Kidney Damage During ex Vivo Preservation
    (2024) Veloso-Gimenez, Valentina; Cardenas-Calderon, Camila; Castillo, Valentina; Carvajal, Felipe; Gallardo-Aguero, Daniela; Gonzalez-Itier, Sergio; Corrales-Orovio, Rocio; Becerra, Daniela; Miranda, Miguel; Rebolledo, Rolando; San Martin, Sebastian; Boric, Mauricio P.; Egana, Jose Tomas
    Several clinical issues are associated with reduced oxygen delivery to tissues due to impaired vascular perfusion; moreover, organs procured for transplantation are subjected to severe hypoxia during preservation. Consequently, alternative tissue oxygenation is an active field in biomedical research where several innovative approaches have been recently proposed. Among these, intravascular photosynthesis represents a promising approach as it relies on the intrinsic capacity of certain microorganisms to produce oxygen upon illumination. In this context, this work aims at the development of photosynthetic perfusable solutions that could be applied to preserve organs for transplantation purposes. Our findings demonstrate that a biocompatible physiological solution containing the photosynthetic microalgae Chlamydomonas reinhardtii can fulfill the metabolic oxygen demand of rat kidney slices in vitro. Furthermore, intravascular administration of this solution does not induce tissue damage in the rat kidneys. Moreover, kidney slices obtained from these algae-perfused organs exhibited significantly improved preservation after 24 h of incubation in hypoxia while exposed to light, resulting in reduced tissue damage and enhanced metabolic status. Overall, the results presented here contribute to the development of alternative strategies for tissue oxygenation, supporting the use of perfusable photosynthetic solutions for organ preservation in transplantation.
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    Structural domains within the HIV-1 mRNA. and the ribosomal protein S25 influence cap-independent translation initiation
    (2016) Carvajal, Felipe; Vallejos, Maricarmen; Walters, Beth; Contreras, Nataly; Hertz, Marla I.; Olivares, Eduardo; Cáceres, Carlos J.; Pino, Karla; Letelier, Alejandro; López Lastra, Marcelo Andrés; Thompson, Sunnie R.