Cell cycle in the fucus zygote parallels a somatic cell cycle but displays a unique translational regulation of cyclin-dependent kinases.
In eukaryotic cells, the basic machinery of cell cycle control is highly conserved. In particular, many cellular events during cell cycle progression are controlled by cyclin-dependent kinases (CDKs). The cell cycle in animal early embryos, however, differs substantially from that of somatic cells or yeasts. For example, cell cycle checkpoints that ensure that the sequence of cell cycle events is correct have been described in somatic cells and yeasts but are largely absent in embryonic cells. Furthermore, the regulation of CDKs is substantially different in the embryonic and somatic cells. In this study, we address the nature of the first cell cycle in the brown alga Fucus, which is evolutionarily distant from the model systems classically used for cell cycle studies in embryos. This cycle consists of well-defined G1, S, G2, and M phases. The purine derivative olomoucine inhibited CDKs activity in vivo and in vitro and induced different cell cycle arrests, including at the G1/S transition, suggesting that, as in somatic cells, CDKs tightly control cell cycle progression. The cell cycle of Fucus zygotes presented the other main features of a somatic cell cycle, such as a functional spindle assembly checkpoint that targets CDKs and the regulation of the early synthesis of two PSTAIRE CDKs, p32 and p34, and the associated histone H1 kinase activity as well as the regulation of CDKs by tyrosine phosphorylation. Surprisingly, the synthesis after fertilization of p32 and p34 was translationally regulated, a regulation not described previously for CDKs. Finally, our results suggest that the activation of mitotic CDKs relies on an autocatalytic amplification mechanism.
Unité Mixte de Recherche 1931 (Centre National de la Recherche Scientifique and Laboratoires Goëmar), Station Biologique, 29680 Roscoff, France.
F
F
Corellou
C
C
Brownlee
L
L
Detivaud
B
B
Kloareg
F Y
FY
Bouget
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D016203:CDC2 Protein Kinase; D002453:Cell Cycle / Q000502:physiology; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant; D018816:Genes, cdc; D006657:Histones / Q000235:genetics; D007701:Kinetin; D008938:Mitosis; D008969:Molecular Sequence Data; D015739:Nocodazole / Q000494:pharmacology; D010446:Peptide Fragments; D000459:Phaeophyceae / Q000166:cytology* / Q000235:genetics / Q000502:physiology; D010766:Phosphorylation; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011687:Purines / Q000494:pharmacology; D012639:Seeds / Q000166:cytology* / Q000235:genetics / Q000502:physiology; D014443:Tyrosine
D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D006657:Histones; D010446:Peptide Fragments; D011687:Purines; C062418:PSTAIR peptide; D014443:Tyrosine; C090046:olomoucine; D011494:Protein Kinases; C102333:histone H1 kinase; D016203:CDC2 Protein Kinase; D018844:Cyclin-Dependent Kinases; D007701:Kinetin; D015739:Nocodazole