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RNA. 2019 Nov;25(11):1561-1575. doi: 10.1261/rna.072116.119. Epub 2019 Aug 14.

Pol5 is an essential ribosome biogenesis factor required for 60S ribosomal subunit maturation in Saccharomyces cerevisiae.

Author information

1
Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, E-41013, Seville, Spain.
2
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, E-41012, Seville, Spain.
3
Centro de Investigación del Cáncer and Instituto de Biología Molecular y Celular del Cáncer, CSIC-Universidad de Salamanca, E-37007, Salamanca, Spain.
4
Centro de Investigación Biomédica en Red en Cáncer (CIBERONC), CSIC-Universidad de Salamanca, E-37007, Salamanca, Spain.
5
Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, E-41012, Seville, Spain.
6
Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, E-37007, Salamanca, Spain.
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Contributed equally

Abstract

In Saccharomyces cerevisiae, more than 250 trans-acting factors are involved in the maturation of 40S and 60S ribosomal subunits. The expression of most of these factors is transcriptionally coregulated to ensure correct ribosome production under a wide variety of environmental and intracellular conditions. Here, we identified the essential nucleolar Pol5 protein as a novel trans-acting factor required for the synthesis of 60S ribosomal subunits. Pol5 weakly and/or transiently associates with early to medium pre-60S ribosomal particles. Depletion of and temperature-sensitive mutations in Pol5 result in a deficiency of 60S ribosomal subunits and accumulation of half-mer polysomes. Both processing of 27SB pre-rRNA to mature 25S rRNA and release of pre-60S ribosomal particles from the nucle(ol)us to the cytoplasm are impaired in the Pol5-depleted strain. Moreover, we identified the genes encoding ribosomal proteins uL23 and eL27A as multicopy suppressors of the slow growth of a temperature-sensitive pol5 mutant. These results suggest that Pol5 could function in ensuring the correct folding of 25S rRNA domain III; thus, favoring the correct assembly of these two ribosomal proteins at their respective binding sites into medium pre-60S ribosomal particles. Pol5 is homologous to the human tumor suppressor Myb-binding protein 1A (MYBBP1A). However, expression of MYBBP1A failed to complement the lethal phenotype of a pol5 null mutant strain though interfered with 60S ribosomal subunit biogenesis.

KEYWORDS:

MYBBP1A; nucleolus; pre-rRNA processing; ribosomal proteins uL23 and eL27; ribosome biogenesis

PMID:
31413149
PMCID:
PMC6795146
[Available on 2020-11-01]
DOI:
10.1261/rna.072116.119

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