Tesis doctoral de Imke María Willers
Mitochondria are essential organelles in cell physiology, playing key roles in bioenergetics, the execution of the cell death and intracellular signaling by ca2+ and reactive oxygen species (ros). mitochondrial dysfunction is associated with a large number of human pathologies, which include cancer, diabetes and neurodegeneration. It is nowadays accepted that a phenotypic trait of most human carcinomas is the reprogramming of their cellular energetic metabolism from mitochondrial oxidative phosphorylation to an enhanced aerobic glycolysis, the so-called warburg effect. In this scenario, the mitochondrial h+-atp synthase is an essential component both in the transduction of biological energy as well as in the execution of cell death. In fact, the down-regulation of the catalytic subunit of the h+-atp synthase (íY-f1-atpase) is a hallmark of many human carcinomas affording a marker of prognosis and of the response to therapy. Moreover, cancer cells and tumors over-express if1, an inhibitor of the h+-atp synthase. In the present phd thesis we have investigated the molecular mechanisms that control at post-transcriptional levels the expression of human íY-f1-atpase. We illustrate that down-regulation of íY-f1-atpase in human breast, lung, esophageal and colon cancer originates from a specific translation repression event that can be recapitulated in in vitro translation assays. We demonstrate that the human 3¿utr of íY-f1-atpase mrna (íY-mrna) is an important cis-acting element necessary for efficient translation. However, and at variance with previous findings with the rat transcript, recapitulation of translational repression requires the participation of additional cis-acting elements of the human transcript. in order to characterize the molecular mechanisms that underlie the masking of íY-mrna we have undertaken studies aimed at the identification of the rna binding proteins and mirnas that target the human transcript. Herein, we demonstrate that ras-gap sh3 binding protein 1 (g3bp1) interacts within the cellular context with the 3¿utr of íY-mrna and is part of the cytoplasmic rna granules that contain íY-mrna. Furthermore, we show that g3bp1 promotes the repression of íY-mrna translation both in vivo and in vitro. Specifically, we demonstrate that g3bp1 hampers the initiation step of íY-mrna translation, strongly supporting that the regulated binding of g3bp1 to the transcript might be involved in masking the translation of íY-mrna in human cancer. Moreover, we demonstrate in a cohort of 93 breast cancer patients that a high expression of g3bp1 affords a marker of cancer progression, specially providing a reliable indicator of developing metastatic disease within the group of breast cancer patients with a good prognosis as assessed by their metabolic phenotype. In contrast to these findings, we show that the rnabps imp1 and npm1 do not interact with íY-mrna playing no relevant role in íY-f1-atpase biology. Finally, we have developed cellular systems to analyze the role of mirnas in íY-f1-atpase expression. Using these systems we show that íY-mrna is targeted and translationally silenced by mir-127-5p, whereas mir-101, mir-103, mir-186, mir-200b, mir-423-5p and mir-581 have no apparent functional role. mir-127-5p is not expressed in human cancer cell lines. However, we observed its expression in human fetal liver strongly suggesting that it might play a relevant role controlling the translation of íY-mrna during development of the human liver.
Datos académicos de la tesis doctoral «Molecular mechanisms controlling the translation of the mrna encoding the human catalytic beta-subunit of mitochondrial h+-atp synthase in cancer an development.«
- Título de la tesis: Molecular mechanisms controlling the translation of the mrna encoding the human catalytic beta-subunit of mitochondrial h+-atp synthase in cancer an development.
- Autor: Imke María Willers
- Universidad: Autónoma de Madrid
- Fecha de lectura de la tesis: 17/06/2011
Dirección y tribunal
- Director de la tesis
- José Manuel Cuezva Marcos
- Tribunal
- Presidente del tribunal: jorgina Satrústegui gil-delgado
- José Antonio Enríquez domínguez (vocal)
- José Luis Rodríguez peralto (vocal)
- Alberto Muñoz terol (vocal)