RNases presented at Protein Society Symposium in Zurich

During the VIII European Symposium of The Protein Society that took place this June in Zurich, Rute Matos, PhD student at the Control of Gene Expression Laboratory received an Award for Scientific Merit for her poster presentation. Around 600 scientific posters were presented at this symposium.

Abstract

Functional and Structural Characterization of RNase II-family of enzymes

Rute G. Matos1, Ana Barbas1, Filipa P. Reis1, Susana Domingues1, Mónica Amblar1,2, Eduardo López-Viñas3, Paulino Goméz Puertas3 and Cecília M. Arraiano1

1.ITQB-Instituto de Tecnologia Química e Biológica/Universidade Nova de Lisboa, Oeiras, Portugal; 2.Present Adress: Unidad de Investigación. Instituto de Salud Carlos III, Madrid, Spain; 3.Centro de Biologia Molecular “Severo Ochoa”, Campus Universidad Autonoma de Madrid and CIBER-Obn, Physiopathology of Obesity and Nutrition, Instituto de Salud Carlos III, Madrid, Spain

RNase II is the prototype of a ubiquitous family of highly processive hydrolytic exoribonucleases that are involved in the maturation, turnover, and quality control of RNA. The members of this family of enzymes can act independently or as a component of the exosome, an essential RNA-degrading multiprotein complex.
The resolution of the crystal structure of E. coli RNase II showed that this enzyme is constituted by four domains: two N-terminal CSD and one C-terminal S1 domain involved in RNA binding, and a central catalytic RNB domain. In order to compare RNase II with other homologues, we presented for the first time the models of two members of the RNase II family, RNase R from E. coli and human Rrp44p/Dis3p. Our results clearly indicate that these three enzymes share a common 3D arrangement, being all the critical residues for exoribonucleolytic activity located in equivalent spatial positions.
Comparing the three protein models it is noteworthy that they have a common arrangement of the tyrosine amino acid involved in the “clamping” of the RNA bound in the catalytic region.  We have demonstrated that this residue is very important for the establishment of the final end-product. We have also shown that the presence of Phe358 is exclusive to E. coli RNase II, what could explain some characteristics of the RNA degradation mechanism that are specific of E. coli RNase II. The active site is formed by four highly conserved aspartates with different roles in catalysis, with Asp209 being the only critical residue for the activity of the enzyme without affecting the ability to bind to the RNA.
Although RNase II, RNase R and Rrp44p all share the same basic organization, there are important differences in their activities, namely the presence of a second nuclease domain apart from the RNB catalytic domain that confers an endonucleolytic activity to Rrp44p. This activity is located in the PINc domain and confers different properties to the full length protein.
The ability of RNase R to act on highly structured RNAs leads to important physiological consequences. Several studies have shown that this protein is involved in the modulation of the expression of virulence in a number of organisms. In order to better understand the virulence mechanisms of two pathogenic organisms (Salmonella typhimurium and Streptococcus pneumoniae) we have initially characterized the RNase II-family of proteins in terms of their exoribonucleolytic activity and RNA binding ability. Further studies are necessary to help understand the RNA decay mechanisms for all these proteins of the RNase II family.