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Mol Cell Biol September 1, 2011; 31 (18): 3857-70.

The midblastula transition defines the onset of Y RNA-dependent DNA replication in Xenopus laevis.

Collart C , Christov CP , Smith JC , Krude T .

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.

PubMed ID: 21791613
PMC ID: PMC3165727
Article link: Mol Cell Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: cdt1 orc2 rny3
Morpholinos: orc2 MO1 orc2 MO2 rny3 MO1 rny4 MO1 rny5 MO1 rnyalpha MO1

References [+] :
Aladjem, Replication in context: dynamic regulation of DNA replication patterns in metazoans. 2007, Pubmed