INVOLVEMENT OF SUMO CONJUGATION IN snRNA BIOGENESIS

BRAGADO, LAUREANO; MAGALNIK, MELINA; SREBROW, ANABELLA

Congreso; 55th Annual Meeting Agentine Society for Biochemistry and Molecular Biology LV Reunion Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2019

In addition to protein-coding genes, RNA polymerase II (Pol II) transcribes numerous genes that correspond to non-coding RNAs, including those of small nuclear RNAs (snRNAs). snRNAs are not only a fundamental component of the spliceosome, but also some of them are necessary for the transcriptional activity of Pol II, as well as for maintaining cellular homeostasis. Although the functions of snRNAs are well understood, the regulation of their biogenesis is still a matter of deep investigation. snRNA genes share common features with protein-coding genes, including the relative positioning of elements that control transcription and RNA processing. However, there are important differences in the set of proteins required for the proper expression and metabolism of these two gene types. SUMOylation is a reversible post-translational modification consisting in the conjugation of SUMO (small ubiquitin-related modifier) to different target proteins. It mainly regulates intra- and inter- molecular interactions, and consequently, the function of a great variety of cellular proteins. A few years ago, we reported the influence of SUMOylation of spliceosomal protein components on spliceosome assembly and catalytic activity. Currently, we are studying the involvement of SUMO conjugation in snRNA biogenesis. So far, we have observed that modifying the levels of global SUMOylation in cultured mammalian cells alters the proportion of nascent vs. mature snRNAs measured by RT-qPCR. Furthermore, we have shown that the transcription factor SNAP43 and the 3´-end processing factor INTS11, both required for snRNA biogenesis, are modified by SUMO, and we have identified the target residues of this modification, allowing us to generate SUMOylation deficient mutants of these two factors. The SNAP43 SUMOylation mutant fails to activate transcription of snRNAs and, intriguingly, leads to cell death in a dominant-negative manner. On the other hand, the INTS11 mutant is unable to achieve 3? end processing of precursor snRNAs. Thus, SUMO conjugation clearly is involved in the regulation of snRNA biogenesis, warranting further investigation