Characterization of Arabidopsis thaliana E3-ubiquitin-ligase SINA-L7, a potential mediator of a RRM and its interaction with GAPC

DIEGO PERALTA; JULIETA BARCHIESI; ALEJANDRO ARAYA; DIEGO GOMEZ-CASATI; MA. VICTORIA BUSI

Congreso; 8th International Conference for Plant Mitochondrial Biology ICPMB; 2013

Arabidopsis Seven in absentia like 7 (SINA-L7), belonging to the seven in absentia family is a putative Zinc finger (SIAH-like) nuclear- cytosolic protein that express in various growth stages and almost all plant tissues. Its homolog was first identified in Drosophila associated with the development of photoreceptors, cell cycle arrest and protein polyubiquitination. Previously, we found SINA-L7 expression altered in three different lines of plants displaying mitochondrial dysfunction what turns SINA-L7 a potential mediator of a RRM. Particularly, SINA-L7 is induced in gapc-1 knock out plants. It has been postulated that the glycolytic enzyme GAPC, also found in the nucleus and associated to the mitochondrial external membrane in plants, may have other important roles. However, little is known about these possible secondary functions, in higher plants. It was recently reported that human and murine GAPC binds an E3-ligase and is translocated to the nucleus. In this context, we face the characterization of SINA-L7 and study its interaction with GAPC in vitro. Results show that SINA-L7 is highly expressed in tissues with active cell division, follows a circadian rhythm and UV exposure doubles its expression. Furthermore, using an ubiquitination assay we found that SINA-L7 has E3-ligase activity and that residue K124 is involved in such process. In addition, SINA-L7 physically interacts with GAPC by pull down analysis and residue K231 in GAPC is responsible of its interaction.