p53 absence increases Heme Oxygenase 1 levels evidencing a crosstalk between different stress pathways in pluripotent stem cells

AYELEN TORO; NICOLAS ANSELMINO; CLAUDIA SOLARI; CAMILA VAZQUEZ ECHEGARAY; VICTORIA PETRONE; MARCOS FRANCIA; ELBA VAZQUEZ; ALEJANDRA GUBERMAN

Mar del Plata

Congreso; LIX Reunión Anual de la Sociedad Argentina de Investigación Clínica; 2019

Embryonic stem cells (ESCs) are pluripotent stem cells (PSCs) derived from the inner cell mass of blastocyst. PSCs are widely exploited to model early embryo development and are a great promise in the regenerative medicine field. It is well known that ESCs possess a fine tuned reactive oxygen species (ROS) balance. This is highly relevant for genome integrity maintenance required for pluripotency and differentiation, and consequently for proper development. Heme Oxygenase 1 (HO-1) is an antioxidant protein essential to redox homeostasis and it was suggested to have also an unknown nuclear function, different from its enzymatic activity. On the other hand, it was proposed that p53 influences ROS balance besides its classical function in response to DNA damage. Although the relationship between these proteins has been explored, little is known about their connection in PSCs. To explore the crosstalk between HO-1 and p53 in PSCs, in this work, we focused in HO-1 gene regulation by p53 in ESCs. We have previously found that HO-1 protein levels were increased in a p53-/- ESC line generated in our lab. Notably, RNA levels were not altered suggesting that HO-1 protein stability is regulated by p53 in ESC. To delve into the mechanism involved we evaluated the effect of protein inhibition by cycloheximide in HO-1 gene modulation, both in wild type (wt) and p53-/- ESCs and found higher HO-1 half-life in the knockout cell line. Remarkably, HO-1 transcription increased in response to hemin treatment, a widely used pharmacological HO-1 gene inductor, and to differentiation stimulus in p53-/- cells similar to wt. These results evidence different levels of HO-1 gene regulation in ESCs. We are currently studying if the differential HO-1 protein stability found involves a p53-dependent proteasome-mediated proteolysis. A p53-HO-1 crosstalk could evidence a link between different stress response pathways relevant to ESC survival and differentiation.