CHARACTERIZATION OF SEVERAL P8 INTERACTING PROTEINS

NEME TAUIL, R; VARONE, C.; MORENO, S.|

Carlos Paz, Cordoba, Argentina

Congreso; XLIV Reunion Anual SAIB; 2008

Sociedad Argentina de Biquimica y Biolgia Molecular

Human p8 is an 82 aminoacid protein expressed in response to stress. It is proposed to be involved in tumour development and acts as growth factor. Previous results show that p8 localises to the nucleus in subconfluent cell cultures and throughout the whole cell under superconfluence. p8 was found to have a nuclear localisation signal (NLS). Two-hybrid system permitted us to identify several of its partners, among which we chose to study the small GTPase Ran as well as one of its accessory proteins, RanBP1, since they are involved in nuclear transport. Pull down technique confirmed that both proteins directly interact with p8. The strength of the interaction with these partners as well as and XM_496217, was compared using a two-hybrid approach. Weprothymosin generated site-directed lysine p8-mutants that proved to be less prone to degradation. Consistent with this fact, they appeared to have a more stable interaction with all tested partners. Confocal microscopy confirmed co-localisation of p8 and Ran in the nucleus. Although p8 mutants also co-localised with Ran, its concentration was increased in the cytoplasm in subconfluent cultures. Preliminary results led us to speculate that p8 levels may respond to a balance of degradation by ubiquitination and stabilization by SUMOylation, two posttraslational modifications that require lysines