title: The midblastula transition defines the onset of Y RNA-dependent DNA replication in Xenopus laevis.
abstract: Noncoding Y RNAs are essential for the initiation of chromosomal DNA replication in mammalian cell extracts, but their role in this process during early vertebrate development is unknown. Here, we use antisense morpholino nucleotides (MOs) to investigate Y RNA function in Xenopus laevis and zebrafish embryos. We show that embryos in which Y RNA function is inhibited by MOs develop normally until the midblastula transition (MBT) but then fail to replicate their DNA and die before gastrulation. Consistent with this observation, Y RNA function is not required for DNA replication in Xenopus egg extracts but is required for replication in a post-MBT cell line. Y RNAs do not bind chromatin in karyomeres before MBT, but they associate with interphase nuclei after MBT in an origin recognition complex (ORC)-dependent manner. Y RNA-specific MOs inhibit the association of Y RNAs with ORC, Cdt1, and HMGA1a proteins, suggesting that these molecular associations are essential for Y RNA function in DNA replication. The MBT is thus a transition point between Y RNA-independent and Y RNA-dependent control of vertebrate DNA replication. Our data suggest that in vertebrates Y RNAs function as a developmentally regulated layer of control over the evolutionarily conserved eukaryotic DNA replication machinery.
authors.affiliation: Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, United Kingdom.
authors.forename: Clara
authors.initials: C
authors.lastname: Collart
authors.forename: Christo P
authors.initials: CP
authors.lastname: Christov
authors.forename: James C
authors.initials: JC
authors.lastname: Smith
authors.forename: Torsten
authors.initials: T
authors.lastname: Krude
mesh_terms: D000818:Animals; D036703:Blastula / Q000166:cytology / Q000502:physiology*; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D025741:HMGA1a Protein / Q000378:metabolism; D009025:Morpholines; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D051738:Origin Recognition Complex / Q000378:metabolism; D058727:RNA, Small Untranslated / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins / Q000378:metabolism; D014982:Xenopus laevis / Q000196:embryology; D015027:Zebrafish
chemical_list: C406819:Cdt1 protein, Xenopus; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D009025:Morpholines; D016376:Oligonucleotides, Antisense; D051738:Origin Recognition Complex; D058727:RNA, Small Untranslated; D029867:Xenopus Proteins; D025741:HMGA1a Protein