title: A comparative study of nucleostemin family members in zebrafish reveals specific roles in ribosome biogenesis.
abstract: Nucleostemin (NS) is an essential protein for the growth and viability of developmental stem cells. Its functions are multi-faceted, including important roles in ribosome biogenesis and in the p53-induced apoptosis pathway. While NS has been well studied, the functions of its family members GNL2 and GNL3-like (GNL3L) remain relatively obscure despite a high degree of sequence and domain homology. Here, we use zebrafish lines carrying mutations in the ns family to compare and contrast their functions in vertebrates. We find the loss of zebrafish ns or gnl2 has a major impact on 60S large ribosomal subunit formation and/or function due to cleavage impairments at distinct sites of pre-rRNA transcript. In both cases this leads to a reduction of total protein synthesis. In contrast, gnl3l loss shows relatively minor rRNA processing delays that ultimately have no appreciable effects on ribosome biogenesis or protein synthesis. However, the loss of gnl3l still results in p53 stabilization, apoptosis, and lethality similarly to ns and gnl2 loss. The depletion of p53 in all three of the mutants led to partial rescues of the morphological phenotypes and surprisingly, a rescue of the 60S subunit collapse in the ns mutants. We show that this rescue is due to an unexpected effect of p53 loss that even in wild type embryos results in an increase of 60S subunits. Our study presents an in-depth description of the mechanisms through which ns and gnl2 function in vertebrate ribosome biogenesis and shows that despite the high degree of sequence and domain homology, gnl3l has critical functions in development that are unrelated to the ribosome.
authors.affiliation: Hubrecht Institute, KNAW and University Medical Center Utrecht, Uppsalalaan 8, 3584CT Utrecht, The Netherlands. Electronic address: p.essers@hubrecht.eu.
authors.forename: Paul B
authors.initials: PB
authors.lastname: Essers
authors.affiliation: Hubrecht Institute, KNAW and University Medical Center Utrecht, Uppsalalaan 8, 3584CT Utrecht, The Netherlands. Electronic address: t.pereboom@hubrecht.eu.
authors.forename: Tamara C
authors.initials: TC
authors.lastname: Pereboom
authors.affiliation: Hubrecht Institute, KNAW and University Medical Center Utrecht, Uppsalalaan 8, 3584CT Utrecht, The Netherlands. Electronic address: y.goos@hubrecht.eu.
authors.forename: Yvonne J
authors.initials: YJ
authors.lastname: Goos
authors.affiliation: Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, D-01307 Dresden, Germany. Electronic address: paridaen@mpi-cbg.de.
authors.forename: Judith T
authors.initials: JT
authors.lastname: Paridaen
authors.affiliation: Hubrecht Institute, KNAW and University Medical Center Utrecht, Uppsalalaan 8, 3584CT Utrecht, The Netherlands. Electronic address: a.macinnes@hubrecht.eu.
authors.forename: Alyson W
authors.initials: AW
authors.lastname: Macinnes
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D005804:Genes, Lethal; D016158:Genes, p53; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D016133:Polymerase Chain Reaction; D012335:RNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000502:physiology*; D015027:Zebrafish / Q000196:embryology; D029961:Zebrafish Proteins / Q000502:physiology*
chemical_list: D017931:DNA Primers; D009687:Nuclear Proteins; D012335:RNA, Ribosomal; D029961:Zebrafish Proteins
keywords: Nucleostemin; Ribosome biogenesis; p53