Full text
| |
| Author(s): |
Daniela Campos Granato
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2007-12-07 |
| Examining board members: |
Carla Columbano de Oliveira;
Gustavo Henrique Goldman;
Suely Lopes Gomes;
Sérgio Verjovski Almeida;
Lucile Maria Floeter Winter
|
| Advisor: | Carla Columbano de Oliveira |
| Abstract | |
In eukaryotes, the rRNA processing depends on several factors, such as, endonucleases, exonucleases, RNA helicases, rRNA modifying enzymes and components of the snoRNPs. With the purpose of characterizing new proteins involved in pre-rRNA processing, Nop53p was identified interacting with the nucleolar protein Nop17p in a two hybrid assay. The conditional yeast strain containing the sequence of the ORF NOP53 under the control of the galactose promoter cannot grow in medium containing glucose, indicating that the protein is essential for cell viability. The results of this work demonstrate that Nop53p is involved in the initial steps of pre-rRNA processing and in the cleavages responsible for the formation of the mature rRNAs 5.8S and 25S. A more detailed analysis of the pre-rRNA processing, by Northern blot and pulse-chase labeling, revealed that Nop53p affects the processing of the 27S precursor, that originates the rRNAs 5.8S and 25S. Nop53p participates in the processing of these RNAs by affecting the polyadenylation of the precursors of the rRNAs 5.8S and 25S. RNA co-imunoprecipitation assays with the fusion protein A-Nop53p confirmed the involvement of Nop53p in the processing of the 27S pre-rRNA, indicating that the protein may interact directly with the RNA. The capacity of Nop53p to bind RNA was confirmed by in vitro assays, while chromatin imunoprecipitation assays demonstrated that Nop53p binds the 5.8S rRNA co- transcriptionally. Nop53p regulates the function of the exosome by interacting directly with the exclusively nuclear subunit of the complex, Rrp6p. (AU) | |