“From the role of SRSF1 as a component of the sumo conjugation pathway to the involvement of Akt SUMOylation in splicing regulation”

GUILLERMO RISSO; FEDERICO PELISCH; BERTA POZZI; ANABELLA SREBROW

Congreso;  “Gene Expression and RNA Processing” (ICGEB-ANPCYT-CONICET); 2011

ICGEB-ANPCYT-CONICET

A cell generates complex responses upon a variety of stimuli that it receives within a multicellular organism. Our lab studies the molecular mechanisms by which different extracellular cues activate signaling pathways that control splicing factor activity at different steps of gene expression regulation. Based on our previous results demonstrating that: i) Pi3K/Akt pathway regulates alternative splicing; ii) Akt phosphorylates SR proteins, in particular SRSF1 (previously known as SF2/ASF); and iii) SRSF1 regulates SUMOylation, we proposed to explore a possible regulatory feedback loop among the components of the Pi3K/Akt/SR protein axis. We found that Akt1 and 2 are SUMOylation targets, as demonstrated by purification of SUMOylated proteins from His-SUMO over-expressing cells by Ni2+ affinity chromatography. We evaluated the effect of over-expressing different SUMO E3 ligases on Akt SUMOylation. Interestingly, SRSF1 is capable of regulating Akt SUMOylation and phosphorylation levels. In the other hand, we found that SRSF1 is also a SUMOylation target and, by using SRSF1 deletion mutants we mapped the SUMO conjugation residue to the RRM2 domain. Worth noticing, our previous results have shown that this domain is responsible for the SUMOylation enhancing activity of SRSF1. We propose to explore the consequences of this previously unknown SRSF1 post-translational modification on the different activities of this multifaceted protein.