SUMOylation and the oncogenic E17K mutation affect AKT1 subcellular distribution and impact on NANOG-binding dynamics to chromatin in embryonic stem cells.

MARCOS GABRIEL FRANCIA, CAMILA OSES, SABRINA LORENA ROBERTI, MORA RENEÉ GARCIA, LUCAS HELIO COZZA, MARIA CANDELARIA DIAZ, VALERIA LEVI, ALEJANDRA SONIA GUBERMAN

Congreso; Stem Cell Niche 2023; 2023

AKT/PKB is a serine-threonine kinase that mediates the action ofa wide range of stimuli, regulating diverse processes in various celltypes. In embryonic stem cells (ESCs), AKT plays a central role inmaintaining pluripotency, specially promoting the expression ofNanog, a key transcription factor. AKT activation depends on itsrecruitment to the cellular membrane and subsequent phosphorylation,as well as other post-translational modifications (PTMs), includingconjugation to the small ubiquitin-related modifier (SUMO),which altogether fine-tune its activity and target specificity.Previous reports indicate that SUMOylation can affect the distributionand accumulation of other proteins in different compartments.In this work, we aimed to investigate the effects of SUMOylation onAKT1 in mouse ESCs. Specifically, we hypothesized that SUMOylationcould affect the subcellular distribution of AKT, its interactionand affinity for its targets, and ultimately impacting in its functionTo explore this hypothesis, we generated mCherry-fused proteinsof AKT1 variants with different SUMOylation capability and analyzedthem by confocal microscopy. We found that this PTM impactsin the distribution and heterogeneity of AKT1 in the nucleus andcytoplasm, and also affects the chromatin-binding dynamics ofNANOG, as revealed by Fluorescence Correlation Spectroscopy.Remarkably, the oncogenic E17K AKT1 mutant in ESCs producedmajor changes, increasing the binding of NANOG to its targets in aSUMOylation-dependent manner. These findings demonstrate thatSUMOylation modulates AKT1 subcellular distribution, adding anextra layer of regulation to its function.