Spb4p, an essential putative RNA helicase, is required for a late step in the assembly of 60S ribosomal subunits in Saccharomyces cerevisiae
Spb4p is a putative ATP-dependent RNA helicase that is required for synthesis of 60S ribosomal subunits. Polysome analyses of strains genetically depleted of Spb4p or carrying the cold-sensitive spb4-1 mutation revealed an under-accumulation of 60S ribosomal subunits. Analysis of pre-rRNA processing...
| Autores: | , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 1998 |
| País: | España |
| Institución: | Universidad de Sevilla (US) |
| Repositorio: | idUS. Depósito de Investigación de la Universidad de Sevilla |
| OAI Identifier: | oai:idus.us.es:11441/143567 |
| Acceso en línea: | https://hdl.handle.net/11441/143567 https://doi.org/10.1017/S1355838298981158 |
| Access Level: | acceso abierto |
| Palabra clave: | DEAD-box proteins Pre-rRNA processing Ribosome biogenesis Yeast |
| Sumario: | Spb4p is a putative ATP-dependent RNA helicase that is required for synthesis of 60S ribosomal subunits. Polysome analyses of strains genetically depleted of Spb4p or carrying the cold-sensitive spb4-1 mutation revealed an under-accumulation of 60S ribosomal subunits. Analysis of pre-rRNA processing by pulse-chase labeling, northern hybridization, and primer extension indicated that these strains exhibited a reduced synthesis of the 25S/5.8S rRNAs, due to inhibition of processing of the 27SB pre-rRNAs. At later times of depletion of Spb4p or following transfer of the spb4-1 strain to more restrictive temperatures, the early pre-rRNA processing steps at sites A0, A1, and A2 were also inhibited. Sucrose gradient fractionation showed that the accumulated 27SB pre-rRNAs are associated with a high-molecular-weight complex, most likely the 66S pre-ribosomal particle. An HA epitope-tagged Spb4p is localized to the nucleolus and the adjacent nucleoplasmic area. On sucrose gradients, HA-Spb4p was found almost exclusively in rapidly sedimenting complexes and showed a peak in the fractions containing the 66S pre-ribosomes. We propose that Spb4p is involved directly in a late and essential step during assembly of 60S ribosomal subunits, presumably by acting as an rRNA helicase. |
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