Poster abstracts

Poster number 13 submitted by Stephanie Biedka

Do ribosomal proteins function in multiple stages of 60S subunit assembly?

Stephanie Biedka (Department of Biological Sciences, Carnegie Mellon University), Hailey Brown (Department of Biological Sciences, Carnegie Mellon University), Jelena Jakovljevic (Department of Biological Sciences, Carnegie Mellon University), John Woolford (Department of Biological Sciences, Carnegie Mellon University)

Abstract:
Assembly of the structural domains of eukaryotic 60S ribosomal subunits occurs in a hierarchical fashion. Previous studies in which individual yeast large subunit ribosomal proteins (RPLs) were depleted revealed that these mutants fell into either early, middle, or late phenotypic classes, as assayed by precursor ribosomal RNA (pre-rRNA) processing and preribosome composition. While this initial approach was critical in the development of the hierarchical model, its main shortcoming is that many RPLs contact more than one domain of the large subunit, and depletion does not allow us to determine if a given RPL functions in more than one stage of assembly. L7 (uL30) and L20 (eL20) are two such RPLs that contact multiple rRNA domains in the mature large subunit. To begin addressing whether they might play roles in multiple stages of assembly, we are making site-directed mutations in L7 and L20. These RPLs are known to function early in large subunit assembly, but their proximity to 5S rRNA in the mature large subunit suggests that L7 and L20 could also function in later stages of assembly. Our site-directed mutations focus on disrupting the interactions between these RPLs and both 5S and 25S rRNA, allowing us to investigate the importance of the contacts that L7 and L20 make with 5S and 25S rRNA. We are studying the effects of these mutations on growth, pre-rRNA processing, preribosome composition, and RNA structure in order to determine if L7 and L20 might have additional roles later in large subunit assembly in addition to their known early roles.

Keywords: yeast ribosome assembly, preribosomes