ZFIN ID: ZDB-PUB-121102-7
Rereplication in emi1-Deficient Zebrafish Embryos Occurs through a Cdh1-Mediated Pathway
Robu, M.E., Zhang, Y., and Rhodes, J.
Date: 2012
Source: PLoS One   7(10): e47658 (Journal)
Registered Authors: Rhodes, Jennifer
Keywords: Embryos, Cyclins, Cell cycle and cell division, Morpholino, Zebrafish, Cell death, Cell cycle inhibitors, DNA replication
MeSH Terms:
  • Animals
  • Cadherins/metabolism*
  • Cell Cycle/drug effects
  • Cell Cycle Proteins/deficiency*
  • Cell Cycle Proteins/metabolism
  • Cell Size/drug effects
  • Cyclin A/metabolism
  • Cyclin B/metabolism
  • DNA Replication*/drug effects
  • Embryo, Nonmammalian/cytology
  • Embryo, Nonmammalian/drug effects
  • Embryo, Nonmammalian/metabolism*
  • Gene Knockdown Techniques
  • Humans
  • Morpholinos/pharmacology
  • Phenotype
  • Signal Transduction*/drug effects
  • Time Factors
  • Zebrafish/embryology*
  • Zebrafish/metabolism*
  • Zebrafish Proteins/deficiency
  • Zebrafish Proteins/metabolism*
PubMed: 23082190 Full text @ PLoS One
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ABSTRACT

Disruption of early mitotic inhibitor 1 (Emi1) interferes with normal cell cycle progression and results in early embryonic lethality in vertebrates. During S and G2 phases the ubiquitin ligase complex APC/C is inhibited by Emi1 protein, thereby enabling the accumulation of Cyclins A and B so they can regulate replication and promote the transition from G2 phase to mitosis, respectively. Depletion of Emi1 prevents mitotic entry and causes rereplication and an increase in cell size. In this study, we show that the developmental and cell cycle defects caused by inactivation of zebrafish emi1 are due to inappropriate activation of APC/C through its cofactor Cdh1. Inhibiting/slowing progression into S-phase by depleting Cdt1, an essential replication licensing factor, partially rescued emi1 deficiency-induced rereplication and the increased cell size. The cell size effect was enhanced by co-depletion of cell survival regulator p53. These data suggest that the increased size of emi1-deficient cells is either directly or indirectly caused by the rereplication defects. Moreover, enforced expression of Cyclin A partially ablated the rereplicating population in emi1-deficient zebrafish embryos, consistent with the role of Cyclin A in origin licensing. Forced expression of Cyclin B partially restored the G1 population, in agreement with the established role of Cyclin B in mitotic progression and exit. However, expression of Cyclin B also partially inhibited rereplication in emi1-deficient embryos, suggesting a role for Cyclin B in regulating replication in this cellular context. As Cyclin A and B are substrates for APC/C-Cdh1 - mediated degradation, and Cdt1 is under control of Cyclin A, these data indicate that emi1 deficiency-induced defects in vivo are due to the dysregulation of an APC/C-Cdh1 molecular axis.

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