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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

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


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.


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

[Available on 2020-11-01]

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