Heterochromatin Protein 1alpha distribution and NANOG-binding dynamics to the chromatin are affected by AKT1 in a SUMOylation dependent manner.

FRANCIA, MARCOS GABRIEL; OSES, CAMILA; ROBERTI, SABRINA; GARCIA, MORA; COZZA, LUCAS; DIAZ, MARIA CANDELARIA; ROVNER, FEDERICO; ORSINGHER, VICTOR; GRECCO, HERNAN; LEVI, VALERIA; GUBERMAN, ALEJANDRA

Congreso; From Concept to Clinic: Advances in Stem Cell Research ? ISSCR 2023; 2023

AKT is a serine-threonine kinase that regulates diverseprocesses in various cell types. In mouse embryonic stemcells (mESCs), it plays a key role in maintaining pluripotency,specially promoting the expression of the pluripotencytranscription factor (TF) Nanog. AKT activation depends onits recruitment to the plasma membrane and subsequentphosphorylation, as well as other post-translationalmodifications (PTMs), including conjugation to the smallubiquitin-related modifier (SUMO), which altogether fine-tuneits activity and target specificity. In this work, we explored theeffects of SUMOylation on AKT1 distribution and function inmESCs. To this purpose, we generated mCherry-fused AKT1variants with different SUMOylation capability and analyzedtheir distribution by confocal microscopy in mESCs. Wefound that this PTM impacts on the distribution andheterogeneity of AKT1 in the nucleus and cytoplasm.Specifically, both SUMOylation and the E17K mutationpromoted AKT1 nuclear localization. These findings led us tohypothesize that this effect on AKT1 distribution could affectits interaction and affinity for its targets, ultimately impactingin its function. To explore this hypothesis, we studied theeffect of AKT SUMOylatability on the distribution ofHeterochromatin protein 1α by quantitative confocalmicroscopy analysis, and on the dynamic interactions ofNANOG with the chromatin, by Fluorescence CorrelationSpectroscopy. We found that both SUMOylation and theE17K mutation impact on the overall chromatin landscape ofmESCs and affect the chromatin-binding dynamics ofNANOG. Remarkably, the oncogenic E17K AKT1 mutantproduced the most prominent changes in these parameters,particularly increasing the binding of NANOG to its targets ina SUMOylation-dependent manner. These findingsdemonstrate that SUMOylation modulates AKT1 subcellulardistribution, the chromatin landscape, and the TF dynamics,adding an extra layer of regulation to its function in mESCs.