Poster abstracts

Poster number 68 submitted by Salini Konikkat

Investigating the Role of the Nop7-Subcomplex in Assembly of the 60S subunit of Yeast

Salini Konikkat (Dept. of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA-15213), John L. Woolford Jr. (Dept. of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA-15213)

Abstract:
Ribosome assembly is a complex biological process in which ribosomal RNA (rRNA) is transcribed in precursor form, processed, modified, and bound by ribosomal proteins to generate the mature ribosomal subunits. Many trans-acting proteins (~200) called ‘assembly factors’ are essential for ribosome assembly in yeast and higher organisms. To better understand how these assembly factors aid ribosome assembly, our lab has focused on a subset of evolutionarily conserved assembly factors called the ‘A3-factors’ (Nop7, Erb1, Ytm1, Rlp7, Nop15, Cic1, Nop12, Ebp2, Brx1, Has1, Pwp1, Drs1), required for the exonucleolytic processing of the 27SA3 precursor rRNA (pre-rRNA)(2,3).

Our research focuses on three A3 factors Nop7, Erb1, and Ytm1, which form a heterotrimeric subcomplex. Analyses of amino acid sequences of these proteins suggest that they lack enzymatic activity, and are likely to serve as structural proteins. Recent research indicates that the Nop7-subcomplex facilitates pre-rRNA folding by enabling bridging of domains I and III of 25S rRNA via protein-protein and protein-rRNA interactions during formation of tertiary structure of the 60S subunit(1,3). Our goal is to understand the role of Nop7 subcomplex proteins in establishing the structure of pre-ribosomes. We discuss a systematic approach to generate specific protein-protein and protein-RNA interaction mutants and describe effects of the mutations on 60S subunit assembly.

References:
1.Granneman, S., Petfalski, E., Tollervey, D. (2011) A cluster of ribosome synthesis factors regulate pre-rRNA folding and 5.8S rRNA maturation by the Rat1 exonuclease. EMBO J 30: 4006-4019.
2. Sahasranaman, A., Dembowski, J., Strahler, J., Andrews, P., Maddock, J., Woolford, J.L., Jr. (2011) Assembly of Saccharomyces cerevisiae 60S ribosomal subunits: role of factors required for 27SA3 pre-rRNA processing. EMBO J. 30: 4020-4032.
3. Tang, L., Sahasranaman, A., Jakoljevic, J., Schleifman, E., Woolford, J.L. Jr. (2008) Interactions among Ytm1, Erb1, and Nop7 required for the assembly of Nop7-subcomplex in yeast preribosomes. Mol. Biol. Cell. 19: 2844-2856.

Keywords: Ribosome Biogenesis, RNA folding