A Cdc2 dependent checkpoint maintains diploidy in Drosophila

Development ◽  
1996 ◽  
Vol 122 (4) ◽  
pp. 1051-1058 ◽  
Author(s):  
S. Hayashi
Keyword(s):  
Central Nervous System ◽  
Dna Replication ◽  
Polytene Chromosomes ◽  
S Phase ◽  
Regulatory Subunit ◽  
Checkpoint Control ◽  
The Central Nervous System ◽  
Mutant Phenotypes ◽  
High Level ◽  
Diploid Cells

DNA replication in G2 does not normally occur due to the checkpoint control. To elucidate its mechanism, the functions of the escargot and Dmcdc2 genes of Drosophila were studied. When escargot function was eliminated, diploid imaginal cells that were arrested in G2 lost Cyclin A, a regulatory subunit of G2/M cdk, and entered an endocycle. escargot genetically interacted with Dmcdc2 which encodes a catalytic subunit of G2/M cdk. The mutant phenotypes of Dmcdc2 itself was similar to those of escargot: many diploid cells in imaginal discs, salivary glands and the central nervous system entered an endocycle and sometimes formed polytene chromosomes. Since mitotically quiescent abdominal histoblasts still required Dmcdc2 to remain diploid, the inhibitory activity of G2/M cdk on DNA replication appeared to be separable from its activity as the mitosis promoting factor. These results suggest that in G2, escargot is required to maintain a high level of G2/M cdk that actively inhibits the entry into S phase.

scholarly journals Divergent S Phase Checkpoint Activation Arising from Prereplicative Complex Deficiency Controls Cell Survival

2009 ◽  
Vol 20 (17) ◽  
pp. 3953-3964 ◽  
Author(s):  
Eric Lau ◽  
Gary G. Chiang ◽  
Robert T. Abraham ◽  
Wei Jiang
Keyword(s):  
Dna Replication ◽  
Cancer Cells ◽  
S Phase ◽  
Checkpoint Control ◽  
Multiple Cancer ◽  
Checkpoint Activation ◽  
Diploid Cells ◽  
Prereplicative Complex ◽  
Stress Damage ◽  
S Phase Checkpoint

The DNA replication machinery plays additional roles in S phase checkpoint control, although the identities of the replication proteins involved in checkpoint activation remain elusive. Here, we report that depletion of the prereplicative complex (pre-RC) protein Cdc6 causes human nontransformed diploid cells to arrest nonlethally in G1-G1/S and S phase, whereas multiple cancer cell lines undergo G1-G1/S arrest and cell death. These divergent phenotypes are dependent on the activation, or lack thereof, of an ataxia telangiectasia and Rad3-related (ATR)-dependent S phase checkpoint that inhibits replication fork progression. Although pre-RC deficiency induces chromatin structural alterations in both nontransformed and cancer cells that normally lead to ATR checkpoint activation, the sensor mechanisms in cancer cells seem to be compromised such that higher levels of DNA replication stress/damage are required to trigger checkpoint response. Our results suggest that therapy-induced disruption of pre-RC function might exert selective cytotoxic effects on tumor cells in human patients.

scholarly journals Replication of Heterochromatin and Structure of Polytene Chromosomes

2000 ◽  
Vol 20 (17) ◽  
pp. 6308-6316 ◽  
Author(s):  
Thomas J. Leach ◽  
Heather L. Chotkowski ◽  
Michael G. Wotring ◽  
Robert L. Dilwith ◽  
Robert L. Glaser
Keyword(s):  
Temporal Pattern ◽  
Position Effect ◽  
Polytene Chromosomes ◽  
S Phase ◽  
Parental Origin ◽  
Position Effect Variegation ◽  
Replication Forks ◽  
Satellite Sequences ◽  
Effect Variegation ◽  
Diploid Cells

ABSTRACT Heterochromatin is characteristically the last portion of the genome to be replicated. In polytene cells, heterochromatic sequences are underreplicated because S phase ends before replication of heterochromatin is completed. Truncated heterochromatic DNAs have been identified in polytene cells of Drosophila and may be the discontinuous molecules that form between fully replicated euchromatic and underreplicated heterochromatic regions of the chromosome. In this report, we characterize the temporal pattern of heterochromatic DNA truncation during development of polytene cells. Underreplication occurred during the first polytene S phase, yet DNA truncation, which was found within heterochromatic sequences of all fourDrosophila chromosomes, did not occur until the second polytene S phase. DNA truncation was correlated with underreplication, since increasing the replication of satellite sequences with thecycE 1672 mutation caused decreased production of truncated DNAs. Finally, truncation of heterochromatic DNAs was neither quantitatively nor qualitatively affected by modifiers of position effect variegation including the Y chromosome,Su(var)2052 , parental origin, or temperature. We propose that heterochromatic satellite sequences present a barrier to DNA replication and that replication forks that transiently stall at such barriers in late S phase of diploid cells are left unresolved in the shortened S phase of polytene cells. DNA truncation then occurs in the second polytene S phase, when new replication forks extend to the position of forks left unresolved in the first polytene S phase.

scholarly journals The role of personal anxiety in the development of psychophysiological indicators in adolescent athletes

2021 ◽  
Vol 10 (4) ◽  
pp. 30-36
Author(s):  
A. A. Makarova ◽  
O. A. Kharkova
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Reaction Time ◽  
Cognitive Behavioral Therapy ◽  
Behavioral Therapy ◽  
Cognitive Behavioral ◽  
Adolescent Athletes ◽  
Personal Anxiety ◽  
The Central Nervous System ◽  
High Level

Objective: to study the role of personal anxiety in the development of psychophysiological indicators in adolescent athletes.Materials and methods. To study the prevalence of high levels of personal anxiety (hereinafter — LT), as well as to determine the characteristics of psychophysiological indicators, the study involved 23 teenagers — boys and girls who were representatives of different sports. Using the device for psychophysiological testing UPFT-1/30 “Psychophysiologist”, indicators of simple visual-motor reaction and the level of LT on the Spielberg scale were obtained. To assess the impact of changes in high LT levels on psychophysiological indicators, 14 adolescent athletes with a high level of personal anxiety were selected and then divided into 2 groups. The experimental group included adolescents who wanted to participate in an experiment on the use of cognitive behavioral therapy techniques to correct high LT levels; the control group included adolescents with high LT levels who were not trained in cognitive behavioral therapy techniques.Results. Every third adolescent athlete had a high level of LT. Adolescent athletes with a high LT level, in contrast to adolescents with an optimal LT level, were less efficient, and, despite a shorter minimum reaction time, made more mistakes. The dynamics of psychophysiological indicators were observed both in the group with intervention and in the group where no cognitive behavioral therapy techniques were performed; however, after studying the difference in the physiological parameters of the central nervous system in the group where there was a change in LT, and in the group where LT either did not change or increased, we found positive changes. Changes in the LT level led to a decrease in the average reaction time, the minimum reaction time, and an increase in the level of stability of reactions.Conclusions. A high level of LT affects the psychophysiological parameters of the central nervous system in adolescent athletes. The use of cognitive behavioral therapy techniques to normalize the LT level of adolescent athletes leads to an improvement in the physiological parameters of the central nervous system.

The endocycle controls nurse cell polytene chromosome structure during Drosophila oogenesis

Development ◽  
1999 ◽  
Vol 126 (2) ◽  
pp. 293-303 ◽  
Author(s):  
K.J. Dej ◽  
A.C. Spradling
Keyword(s):  
Polytene Chromosome ◽  
Nurse Cell ◽  
Chromosome Structure ◽  
Polytene Chromosomes ◽  
S Phase ◽  
Nurse Cells ◽  
Chromosome Behavior ◽  
M Phase ◽  
Diploid Cells ◽  
Polytene Nuclei

Polytene chromosomes exhibit intricate higher order chromatin structure that is easily visualized due to their precisely aligned component strands. However, it remains unclear if the same factors determine chromatin organization in polyploid and diploid cells. We have analyzed one such factor, the cell cycle, by studying changes in Drosophila nurse cell chromosomes throughout the 10 to 12 endocycles of oogenesis. We find that nurse cells undergo three distinct types of endocycle whose parameters are correlated with chromosome behavior. The first four endocycles support complete DNA replication; poorly banded polytene euchromatin progressively condenses during the late S phases to produce blob-like chromosomes. During the unique fifth endocycle, an incomplete late S phase is followed by a mitosis-like state during which the 64C chromosomes dissociate into 32 chromatid pairs held together by unreplicated regions. All the subsequent endocycles lack any late S phase; during these cycles a new polytene chromosome grows from each 2C chromatid pair to generate 32-ploid polytene nuclei. These observations suggest that euchromatin begins to condense during late S phase and that nurse cell polytene chromosome structure is controlled by regulating whether events characteristic of late S and M phase are incorporated or skipped within a given endocycle.

Cdc18p can block mitosis by two independent mechanisms

1998 ◽  
Vol 111 (20) ◽  
pp. 3101-3108 ◽  
Author(s):  
E. Greenwood ◽  
H. Nishitani ◽  
P. Nurse
Keyword(s):  
Dna Replication ◽  
S Phase ◽  
Checkpoint Control ◽  
Replication Checkpoint ◽  
Mitotic Kinase ◽  
C Terminus ◽  
N Terminus ◽  
Dna Replication Checkpoint ◽  
Checkpoint Genes

The DNA replication checkpoint is required to maintain the integrity of the genome, inhibiting mitosis until S phase has been successfully completed. The checkpoint preventing premature mitosis in Schizosaccharomyces pombe relies on phosphorylation of the tyrosine-15 residue on cdc2p to prevent its activation and hence mitosis. The cdc18 gene is essential for both generating the DNA replication checkpoint and the initiation of S phase, thus providing a key role for the overall control and coordination of the cell cycle. We show that the C terminus of the protein is capable of both initiating DNA replication and the checkpoint function of cdc18p. The C terminus of cdc18p acts upstream of the DNA replication checkpoint genes rad1, rad3, rad9, rad17, hus1 and cut5 and requires the wee1p/mik1p tyrosine kinases to block mitosis. The N terminus of cdc18p can also block mitosis but does so in the absence of the DNA replication checkpoint genes and the wee1p/mik1p kinases therefore acting downstream of these genes. Because the N terminus of cdc18p associates with cdc2p in vivo, we suggest that by binding the cdc2p/cdc13p mitotic kinase directly, it exerts an effect independently of the normal checkpoint control, probably in an unphysiological manner.

scholarly journals H3K9 Promotes Under-Replication of Pericentromeric Heterochromatin in Drosophila Salivary Gland Polytene Chromosomes

Genes ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 93 ◽  
Author(s):  
Robin Armstrong ◽  
Taylor Penke ◽  
Samuel Chao ◽  
Gabrielle Gentile ◽  
Brian Strahl ◽  
...  
Keyword(s):  
Salivary Gland ◽  
Dna Replication ◽  
Polytene Chromosomes ◽  
Cell Types ◽  
Gene Replacement ◽  
Pericentric Heterochromatin ◽  
Replication Initiation ◽  
H3k9 Methylation ◽  
Diploid Cells ◽  
And Function

Chromatin structure and its organization contributes to the proper regulation and timing of DNA replication. Yet, the precise mechanism by which chromatin contributes to DNA replication remains incompletely understood. This is particularly true for cell types that rely on polyploidization as a developmental strategy for growth and high biosynthetic capacity. During Drosophila larval development, cells of the salivary gland undergo endoreplication, repetitive rounds of DNA synthesis without intervening cell division, resulting in ploidy values of ~1350C. S phase of these endocycles displays a reproducible pattern of early and late replicating regions of the genome resulting from the activity of the same replication initiation factors that are used in diploid cells. However, unlike diploid cells, the latest replicating regions of polyploid salivary gland genomes, composed primarily of pericentric heterochromatic enriched in H3K9 methylation, are not replicated each endocycle, resulting in under-replicated domains with reduced ploidy. Here, we employ a histone gene replacement strategy in Drosophila to demonstrate that mutation of a histone residue important for heterochromatin organization and function (H3K9) but not mutation of a histone residue important for euchromatin function (H4K16), disrupts proper endoreplication in Drosophila salivary gland polyploid genomes thereby leading to DNA copy gain in pericentric heterochromatin. These findings reveal that H3K9 is necessary for normal levels of under-replication of pericentric heterochromatin and suggest that under-replication at pericentric heterochromatin is mediated through H3K9 methylation.

scholarly journals Regulation of Initiation of S Phase, Replication Checkpoint Signaling, and Maintenance of Mitotic Chromosome Structures during S Phase by Hsk1 Kinase in the Fission Yeast

2001 ◽  
Vol 12 (5) ◽  
pp. 1257-1274 ◽  
Author(s):  
Tadayuki Takeda ◽  
Keiko Ogino ◽  
Kazuo Tatebayashi ◽  
Hideo Ikeda ◽  
Ken-ichi Arai ◽  
...  
Keyword(s):  
Dna Replication ◽  
Synthetic Lethality ◽  
S Phase ◽  
Regulatory Subunit ◽  
Temperature Sensitive ◽  
Origin Firing ◽  
Replication Checkpoint ◽  
Checkpoint Signaling ◽  
Checkpoint Pathway ◽  
Nuclear Structures

Hsk1, Saccharomyces cerevisiae Cdc7-related kinase in Shizosaccharomyces pombe, is required for G1/S transition and its kinase activity is controlled by the regulatory subunit Dfp1/Him1. Analyses of a newly isolated temperature-sensitive mutant, hsk1-89, reveal that Hsk1 plays crucial roles in DNA replication checkpoint signaling and maintenance of proper chromatin structures during mitotic S phase through regulating the functions of Rad3 (ATM)-Cds1 and Rad21 (cohesin), respectively, in addition to expected essential roles for initiation of mitotic DNA replication through phosphorylating Cdc19 (Mcm2). Checkpoint defect inhsk1-89 is indicated by accumulation ofcut cells at 30°C. hsk1-89 displays synthetic lethality in combination with rad3 deletion, indicating that survival of hsk1-89 depends on Rad3-dependent checkpoint pathway. Cds1 kinase activation, which normally occurs in response to early S phase arrest by nucleotide deprivation, is largely impaired in hsk1-89. Furthermore, Cds1-dependent hyperphosphorylation of Dfp1 in response to hydroxyurea arrest is eliminated in hsk1-89, suggesting that sufficient activation of Hsk1-Dfp1 kinase is required for S phase entry and replication checkpoint signaling.hsk1-89 displays apparent defect in mitosis at 37°C leading to accumulation of cells with near 2C DNA content and with aberrant nuclear structures. These phenotypes are similar to those ofrad21-K1 and are significantly enhanced in ahsk1-89 rad21-K1 double mutant. Consistent with essential roles of Rad21 as a component for the cohesin complex, sister chromatid cohesion is partially impaired in hsk1-89, suggesting a possibility that infrequent origin firing of the mutant may affect the cohesin functions during S phase.

Klk8, a multifunctional protease in the brain and skin: analysis of knockout mice

2010 ◽  
Vol 391 (4) ◽  
Author(s):  
Shigetaka Yoshida
Keyword(s):  
Central Nervous System ◽  
Long Term Potentiation ◽  
Term Potentiation ◽  
The Central Nervous System ◽  
Synaptic Changes ◽  
Adhesive Molecules ◽  
High Level ◽  
Activity Dependent ◽  
The Brain

Abstract Klk8 is a tryptic serine protease with limited substrate specificity. Klk8 mRNA is expressed in many developing organs, whereas its expression is confined to limited regions, including the hippocampus, in adults. In the hippocampus, Klk8 is involved in activity-dependent synaptic changes such as long-term potentiation, which was found to be suppressed in Klk8 knockout (KO) mice. Oligodendrocytes only expressed Klk8 mRNA after injury to the central nervous system. The epidermis of the skin is one of the tissues that exhibits a high level of KLK8 expression. Klk8 might be involved in desquamation through the degradation of adhesive molecules that connect layers of the epidermis. Klk8 might thus be involved in tissue development and rearrangement.

scholarly journals A Fission Yeast Gene,him1+/dfp1+, Encoding a Regulatory Subunit for Hsk1 Kinase, Plays Essential Roles in S-Phase Initiation as Well as in S-Phase Checkpoint Control and Recovery from DNA Damage

1999 ◽  
Vol 19 (8) ◽  
pp. 5535-5547 ◽  
Author(s):  
Tadayuki Takeda ◽  
Keiko Ogino ◽  
Etsuko Matsui ◽  
Min Kwan Cho ◽  
Hiroyuki Kumagai ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Fission Yeast ◽  
Kinase Activity ◽  
S Phase ◽  
Regulatory Subunit ◽  
Checkpoint Control ◽  
Regulatory Subunits ◽  
Hydroxyurea Treatment ◽  
S Phase Checkpoint

ABSTRACT Saccharomyces cerevisiae CDC7 encodes a serine/threonine kinase required for G1/S transition, and its related kinases are present in fission yeast as well as in higher eukaryotes, including humans. Kinase activity of Cdc7 protein depends on the regulatory subunit, Dbf4, which also interacts with replication origins. We have identified him1+ from two-hybrid screening with Hsk1, a fission yeast homologue of Cdc7 kinase, and showed that it encodes a regulatory subunit of Hsk1. Him1, identical to Dfp1, previously identified as an associated molecule of Hsk1, binds to Hsk1 and stimulates its kinase activity, which phosphorylates both catalytic and regulatory subunits as well as recombinant MCM2 protein in vitro. him1+ is essential for DNA replication in fission yeast cells, and its transcription is cell cycle regulated, increasing at middle M to late G1. The protein level is low at START in G1, increases at the G1/S boundary, and is maintained at a high level throughout S phase. Him1 protein is hyperphosphorylated at G1/S through S during the cell cycle as well as in response to early S-phase arrest induced by nucleotide deprivation. Deletion of one of the motifs conserved in regulatory subunits for Cdc7-related kinases as well as alanine substitution of three serine and threonine residues present in the same motif resulted in a defect in checkpoint regulation normally induced by hydroxyurea treatment. The alanine mutant also showed growth retardation after UV irradiation and the addition of methylmethane sulfonate. In keeping with this result, a database search indicates that him1+ is identical to rad35+ . Our results reveal a novel function of the Cdc7/Dbf4-related kinase complex in S-phase checkpoint control as well as in growth recovery from DNA damage in addition to its predicted essential function in S-phase initiation.

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