CHARACTERIZING THE ACTIVITY OF THE SPLICING FACTOR SRSF1 IN THE SUMO CONJUGATION PATHWAY

MAMMI, PABLO; POZZI, BERTA; BRAGADO, LAUREANO; SREBROW, ANABELLA

Buenos Aires

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

The SR family of proteins, widely characterized as regulators ofthe splicing process, share a conserved molecular structure comprising one or two RNA recognition motifs (RRMs) and a serine-arginine rich domain. Some members of this family, and in particular SRSF1, are involved in a wide variety of regulatory functions at different levels of gene expression, being considered multifaceted proteins. Our work is focused on characterizing the E3 SUMO ligase-like activity of SRSF1 that was previously described by our laboratory. In addition to its interaction with enzymes of the SUMO machinery, we identified different substrates whose SUMOylation is regulated by SRSF1, including proteins involved in different aspects of pre-mRNA processing and metabolism. By comparing the SUMOylation-enhancing activity of various members of the SR family, as well as analyzing a variety of deletion mutants, our laboratorypostulated the involvement of SRSF1 RMM2 in the E3 ligase-like activity of this protein. By generating a battery of SRSF1 mutants, we have demonstrated that mutating a particular single residue within the RRM2 domain abolishes the SUMOylation-enhacing activity of this protein while mutating two specific residues within the RRM1 domain exacerbates this function. Interestingly, it has been reported that these two SRSF1 mutants disrupt the RNA binding capacity of this protein by the corresponding domains. These findings suggest a correlation between the SUMOylation E3 ligase-like activity of this splicing factor and its RNA binding ability. As SRSF1-RNA interaction can also mediate the nucleo-citoplasmic shuttling of this protein, it would be interesting to define whether the E3 ligase-like activity of this factor depends on its subcellular/subnuclear localization. Moreover, we are currently characterizing both cellular components as well as cellular conditions that modulate SRSF1 activity along the SUMO pathway