The NIMA-related kinase X-Nek2B is required for efficient assembly of the zygotic centrosome in Xenopus laevis

2000 ◽  
Vol 113 (11) ◽  
pp. 1973-1984 ◽  
Author(s):  
A.M. Fry ◽  
P. Descombes ◽  
C. Twomey ◽  
R. Bacchieri ◽  
E.A. Nigg
Keyword(s):  
Cell Cycle ◽  
Xenopus Laevis ◽  
Basal Body ◽  
Chromatin Condensation ◽  
Embryonic Cells ◽  
Serine Threonine Kinase ◽  
Cell Cycles ◽  
Functional Studies ◽  
Mammalian Cell Cycle ◽  
Egg Extracts

Nek2 is a mammalian cell cycle-regulated serine/threonine kinase that belongs to the family of proteins related to NIMA of Aspergillus nidulans. Functional studies in diverse species have implicated NIMA-related kinases in G(2)/M progression, chromatin condensation and centrosome regulation. To directly address the requirements for vertebrate Nek2 kinases in these cell cycle processes, we have turned to the biochemically-tractable system provided by Xenopus laevis egg extracts. Following isolation of a Xenopus homologue of Nek2, called X-Nek2B, we found that X-Nek2B abundance and activity remained constant through the first mitotic cycle implying a fundamental difference in Nek2 regulation between embryonic and somatic cell cycles. Removal of X-Nek2B from extracts did not disturb either entry into mitosis or the accompanying condensation of chromosomes providing no support for a requirement for Nek2 in these processes at least in embryonic cells. In contrast, X-Nek2B localized to centrosomes of adult Xenopus cells and was rapidly recruited to the basal body of Xenopus sperm following incubation in egg extracts. Recruitment led to phosphorylation of the X-Nek2B kinase. Most importantly, depletion of X-Nek2B from extracts significantly delayed both the assembly of microtubule asters and the recruitment of gamma-tubulin to the basal body. Hence, these studies demonstrate that X-Nek2B is required for efficient assembly of a functional zygotic centrosome and highlight the possibility of multiple roles for vertebrate Nek2 kinases in the centrosome cycle.

scholarly journals Dissection of the XChk1 Signaling Pathway in Xenopus laevis Embryos

2000 ◽  
Vol 11 (9) ◽  
pp. 3101-3108 ◽  
Author(s):  
Nicholas C. Kappas ◽  
Pamela Savage ◽  
Katherine C. Chen ◽  
Allan T. Walls ◽  
Jill C. Sible
Keyword(s):  
Cell Cycle ◽  
Xenopus Laevis ◽  
Signaling Pathway ◽  
Embryonic Cell ◽  
Midblastula Transition ◽  
Cell Cycles ◽  
Cyclin Dependent Kinases ◽  
Xenopus Embryos ◽  
Egg Extracts ◽  
Sperm Nuclei

Checkpoint pathways inhibit cyclin-dependent kinases (Cdks) to arrest cell cycles when DNA is damaged or unreplicated. Early embryonic cell cycles of Xenopus laevis lack these checkpoints. Completion of 12 divisions marks the midblastula transition (MBT), when the cell cycle lengthens, acquiring gap phases and checkpoints of a somatic cell cycle. Although Xenopus embryos lack checkpoints prior to the MBT, checkpoints are observed in cell-free egg extracts supplemented with sperm nuclei. These checkpoints depend upon the Xenopus Chk1 (XChk1)-signaling pathway. To understand why Xenopus embryos lack checkpoints,xchk1 was cloned, and its expression was examined and manipulated in Xenopus embryos. Although XChk1 mRNA is degraded at the MBT, XChk1 protein persists throughout development, including pre-MBT cell cycles that lack checkpoints. However, when DNA replication is blocked, XChk1 is activated only after stage 7, two cell cycles prior to the MBT. Likewise, DNA damage activates XChk1 only after the MBT. Furthermore, overexpression of XChk1 inXenopus embryos creates a checkpoint in which cell division arrests, and both Cdc2 and Cdk2 are phosphorylated on tyrosine 15 and inhibited in catalytic activity. These data indicate that XChk1 signaling is intact but blocked upstream of XChk1 until the MBT.

scholarly journals A molecular marker for centriole maturation in the mammalian cell cycle.

1995 ◽  
Vol 130 (4) ◽  
pp. 919-927 ◽  
Author(s):  
B M Lange ◽  
K Gull
Keyword(s):  
Cell Cycle ◽  
Molecular Marker ◽  
Specific Cell ◽  
Cell Cycles ◽  
Functional Maturation ◽  
Ability To Act ◽  
Molecular Events ◽  
Mammalian Cell Cycle ◽  
A Cell ◽  
First Time

The centriole pair in animals shows duplication and structural maturation at specific cell cycle points. In G1, a cell has two centrioles. One of the centrioles is mature and was generated at least two cell cycles ago. The other centriole was produced in the previous cell cycle and is immature. Both centrioles then nucleate one procentriole each which subsequently elongate to full-length centrioles, usually in S or G2 phase. However, the point in the cell cycle at which maturation of the immature centriole occurs is open to question. Furthermore, the molecular events underlying this process are entirely unknown. Here, using monoclonal and polyclonal antibody approaches, we describe for the first time a molecular marker which localizes exclusively to one centriole of the centriolar pair and provides biochemical evidence that the two centrioles are different. Moreover, this 96-kD protein, which we name Cenexin (derived from the Latin, senex for "old man," and Cenexin for centriole) defines very precisely the mature centriole of a pair and is acquired by the immature centriole at the G2/M transition in prophase. Thus the acquisition of Cenexin marks the functional maturation of the centriole and may indicate a change in centriolar potential such as its ability to act as a basal body for axoneme development or as a congregating site for microtubule-organizing material.

Epigenetic dynamics across the cell cycle

2010 ◽  
Vol 48 ◽  
pp. 107-120 ◽  
Author(s):  
Tony Bou Kheir ◽  
Anders H. Lund
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Cell Cycle Progression ◽  
Current Knowledge ◽  
Chromatin Condensation ◽  
Chromatin Modifications ◽  
Cycle Progression ◽  
Daughter Cells ◽  
Mammalian Cell Cycle ◽  
Regulate Cell Cycle Progression

Progression of the mammalian cell cycle depends on correct timing and co-ordination of a series of events, which are managed by the cellular transcriptional machinery and epigenetic mechanisms governing genome accessibility. Epigenetic chromatin modifications are dynamic across the cell cycle, and are shown to influence and be influenced by cell-cycle progression. Chromatin modifiers regulate cell-cycle progression locally by controlling the expression of individual genes and globally by controlling chromatin condensation and chromosome segregation. The cell cycle, on the other hand, ensures a correct inheritance of epigenetic chromatin modifications to daughter cells. In this chapter, we summarize the current knowledge on the dynamics of epigenetic chromatin modifications during progression of the cell cycle.

scholarly journals Genome-Wide Identification and Analysis of Cell Cycle Genes in Betula pendula

2021 ◽  
Author(s):  
Yijie Li ◽  
Song Chen ◽  
Yuhang Liu ◽  
Haijiao Huang
Keyword(s):  
Cell Cycle ◽  
Growth And Development ◽  
Betula Pendula ◽  
Cell Cycle Progression ◽  
Transcript Abundance ◽  
Cell Cycle Gene ◽  
Specific Expression ◽  
Cell Cycles ◽  
Cell Cycle Genes ◽  
Functional Studies

Research Highlights: This study identified the cell cycle genes in birch that likely play important roles during plant growth and development. This analysis provides a basis for understanding the regulatory mechanism of various cell cycles in Betula pendula. Background and Objectives: The cell cycle factors not only influence cell cycle progression together, but also regulate accretion, division and differentiation of cells, and then regulate growth and development of plant. In this study, we identified the putative cell cycle genes in B. pendula genome, based on the annotated cell cycle genes in A. thaliana. It could serve as a foundation for further functional studies. Materials and Methods: The transcript abundance was determined for all the cell cycle genes in xylem, root, leaf and flower tissues using RNA-seq technology. Results: We identified 59 cell cycle gene models in the genome of B. pendula, 17 highly expression genes among them. These genes were BpCDKA.1, BpCDKB1.1, BpCDKB2.1, BpCKS1.2, BpCYCB1.1, BpCYCB1.2, BpCYCB2.1, BpCYCD3.1, BpCYCD3.5, BpDEL1, BpDpa2, BpE2Fa, BpE2Fb, BpKRP1, BpKRP2, BpRb1 and BpWEE1. Conclusions: We identified 17 core cell cycle genes in the genome of birch by combining phylogenetic analysis and tissue specific expression data.

scholarly journals Single-embryo phosphoproteomics reveals the importance of intrinsic disorder in cell cycle dynamics

2021 ◽  
Author(s):  
Juan Manuel Valverde ◽  
Geronimo Dubra ◽  
Henk van den Toorn ◽  
Guido van Mierlo ◽  
Michiel Vermeulen ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Intrinsically Disordered Proteins ◽  
Protein Complexes ◽  
Disordered Proteins ◽  
Cell Cycles ◽  
Intrinsically Disordered ◽  
Intrinsically Disordered Regions ◽  
Egg Extracts ◽  
Cell Cycle Dynamics

Switch-like cyclin-dependent kinase (CDK)-1 activation is thought to underlie the abruptness of mitotic onset, but how CDKs can simultaneously phosphorylate many diverse substrates is unknown, and direct evidence for such phosphorylation dynamics in vivo is lacking. Here, we analysed protein phosphorylation states in single Xenopus embryos throughout synchronous cell cycles. Over a thousand phosphosites were dynamic in vivo, and assignment of cell cycle phases using egg extracts revealed hundreds of S-phase phosphorylations. Targeted phosphoproteomics in single embryos showed switch-like mitotic phosphorylation of diverse protein complexes. The majority of cell cycle-regulated phosphosites occurred in CDK consensus motifs, and 72% located to intrinsically disordered regions. Dynamically phosphorylated proteins, and documented substrates of cell cycle kinases, are significantly more disordered than phosphoproteins in general. Furthermore, 30-50% are components of membraneless organelles. Our results suggest that phosphorylation of intrinsically disordered proteins by cell cycle kinases, particularly CDKs, allows switch-like mitotic cellular reorganisation.

scholarly journals Genome-Wide Identification and Analysis of Cell Cycle Genes in Betula pendula

2021 ◽  
Author(s):  
Yijie Li ◽  
Song Chen ◽  
Yuhang Liu ◽  
Haijiao Huang
Keyword(s):  
Cell Cycle ◽  
Growth And Development ◽  
Betula Pendula ◽  
Cell Cycle Progression ◽  
Transcript Abundance ◽  
Specific Expression ◽  
Cell Cycles ◽  
Cell Cycle Genes ◽  
Functional Studies ◽  
Genome Wide

Research Highlights: This study identified the cell cycle genes in birch that likely play important roles during plant growth and development. This provides a basis for understanding the regulatory mechanism of various cell cycles in Betula pendula. Background and Objectives: The cell cycle factors not only influence cell cycle progression together, but also regulate accretion, division and differentiation of cells, and then regulate growth and development of plant. In this study, we identified the putative cell cycle genes in B. pendula genome, based on the annotated cell cycle genes in A. thaliana. It could serve as a foundation for further functional studies. Materials and Methods: The transcript abundance was determined for all the cell cycle genes in xylem, root, leaf and flower tissues using RNA-seq technology. Results: We identified 59cell cycle gene models in the genome of B. pendula, 17 highly expression genes among them. These genes were BpCDKA.1, BpCDKB1.1, BpCDKB2.1, BpCKS1.2, BpCYCB1.1, BpCYCB1.2, BpCYCB2.1, BpCYCD3.1, BpCYCD3.5, BpDEL1, BpDpa2, BpE2Fa, BpE2Fb, BpKRP1, BpKRP2, BpRb1 and BpWEE1. Conclusions: We identified 17 core cell cycle genes in the genome of birch by combining phylogenetic analysis and tissue specific expression data.

Characterization of the unusually rapid cell cycles during rat gastrulation

Development ◽  
1993 ◽  
Vol 117 (3) ◽  
pp. 873-883 ◽  
Author(s):  
A. Mac Auley ◽  
Z. Werb ◽  
P.E. Mirkes
Keyword(s):  
Cell Cycle ◽  
Cycle Time ◽  
Mammalian Cells ◽  
Primitive Streak ◽  
Cycle Duration ◽  
Embryonic Cells ◽  
Cell Cycle Time ◽  
Cell Cycles ◽  
A Cell ◽  
Cycle Regulation

The onset of gastrulation in rodents is associated with the start of differentiation within the embryo proper and a dramatic increase in the rate of growth and proliferation. We have determined the duration of the cell cycle for mesodermal and ectodermal cells of rat embryos during gastrulation (days 8.5 to 9.5 of gestation) using a stathmokinetic analysis. These embryonic cells are the most rapidly dividing mammalian cells yet described. Most cells of the ectoderm and mesoderm had a cell cycle time of 7 to 7.5 hours, but the cells of the primitive streak divided every 3 to 3.5 hours. Total cell cycle time was reduced by shortening S and G2, as well as G1, in contrast to cells later in development, when cell cycle duration is modulated largely by varying the length of G1. In the ectoderm and mesoderm, G1 was 1.5 to 2 hours, S was 3.5 to 4 hours, and G2 was 30 to 40 minutes. G1, S and G2 were shortened even further in the cells of the primitive streak: G1 was less than 30 minutes, S was 2 to 2.75 hours, and G2 was less than 20 minutes. Thus, progress of cells through all phases of the cell cycle is extensively modified during rodent embryogenesis. Specifically, the increased growth rate during gastrulation is associated with radical changes in cell cycle structure and duration. Further, the commitment of cells to become mesoderm and endoderm by entering the primitive streak is associated with expression of a very short cell cycle during transit of the primitive streak, such that developmental decisions determining germ layer fate are reflected in differences in cell cycle regulation.

Nuclear distribution of PCNA during embryonic development in Xenopus laevis: a reinvestigation of early cell cycles

1992 ◽  
Vol 102 (1) ◽  
pp. 63-69 ◽  
Author(s):  
M. Leibovici ◽  
G. Monod ◽  
J. Geraudie ◽  
R. Bravo ◽  
M. Mechali
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Xenopus Laevis ◽  
Early Development ◽  
Nuclear Periphery ◽  
S Phase ◽  
Nuclear Antigen ◽  
Midblastula Transition ◽  
Cell Cycles ◽  
Cyclical Pattern

The immunocytological distribution of the proliferating cell nuclear antigen (PCNA), a protein involved in DNA replication, has been examined during the early development of Xenopus laevis. The protein is uniformly detected in nuclei during early stages up to the neurula stage. PCNA is detected by its distinctive cyclical pattern during early development, remaining detectable only during the period of S phase of each cell cycle. Immunological detection of PCNA is therefore a useful and specific non-isotopic marker of S-phase cells in the embryo. PCNA associates with typical karyomeric structures, suggesting that DNA replication starts before the nuclear compartment is entirely formed. At the midblastula transition, a new pattern of PCNA staining becomes apparent. First, a new type of PCNA staining is detected at the nuclear periphery. Second, mitotic clusters with different PCNA distributions suggest that the onset of desynchronization of the cell cycle at this stage is not random.

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