AKT SUMOylation is required for Nanog promoter induction in mouse embryonic stem cells

MARCOS FRANCIA; SOLEDAD COSENTINO; CAMILA VAZQUEZ ECHEGARAY; CLAUDIA SOLARI; AYELEN TORO; VICTORIA PETRONE; ARIEL WAISMAN; LINO BARAÑAO; ALEJANDRA GUBERMAN

CABA

Simposio; Simposio Fronteras en Biociencia 3; 2018

IBIOBA

Embryonic stem cells (ESC) are derived from the inner cell mass ofblastocysts. Under specific culture conditions, they can self-renewindefinitely, preserving their potential to be differentiated to cells of allthree germ layers. This undifferentiated state is mainly maintained by theLeukemia Inhibitory Factor (LIF) added to the serum containing culturemedia. The PI3K/AKT signaling transduction pathway is switched on byLIF and is crucial for the expression and activity of the ESC?s essentialtranscription factors Oct4, Sox2 and Nanog. It has been reported thatmodification of Akt1 by SUMO conjugation regulates the activity of thiskinase, with direct consequences in the splicing pattern, cell growth andsurvival in cultured cell lines. However, the role of this post-translationalmodification (PTM) of Akt1 has not been studied in ESC yet.Our hypothesis is that SUMOylation of Akt1 is relevant for themaintenance of ESC fundamental properties. This work was aimed to studythe effect of this PMT of Akt1 on the activity of the Nanog promoter.We transfected W4 ESC line with expression vectors of Akt1 variants withdifferent capacity of being SUMOylated along with a Luciferase reportervector driven by the Nanog gene promoter.Our results suggest that Akt SUMOylation is required for enhancing theNanog promoter activity. We observed an induction with those variantsthat can be SUMOylated and a complete loss of this effect with those inwhich SUMO conjugation is diminished. With the purpose of studying themolecular mechanism involved, we found that this effect can be observedusing either LIF, LIF&2i or no LIF culture media on W4 wild type cellline. Moreover, we detected the same effect on a W4 p53-KO cell line.Linear Mixed Models was used for testing all comparisons, obtainingstatistically significant differences (p<0.05).Our results suggest that SUMOylation of Akt1 is important for inducingNanog promoter activity and that GSK3-B, p53 and possibly STAT3 arenot responsible for this effect. We are conducting further research tounravel the molecular mechanism involved.