A Drosophila G1-specific cyclin E homolog exhibits different modes of expression during embryogenesis

Development ◽  
1993 ◽  
Vol 119 (3) ◽  
pp. 673-690 ◽  
Author(s):  
H.E. Richardson ◽  
L.V. O'Keefe ◽  
S.I. Reed ◽  
R. Saint

We have isolated a Drosophila homolog of the human G1-specific cyclin E gene. Cyclin E proteins thus constitute an evolutionarily conserved subfamily of metazoan cyclins. The Drosophila cyclin E gene, DmcycE, encodes two proteins with a common C-terminal region and unique N-terminal regions. Unlike other Drosophila cyclins, DmcycE exhibits a dynamic pattern of expression during development. DmcycE is supplied maternally, but at the completion of the cleavage divisions and prior to mitosis 14, the maternal transcripts are rapidly degraded in all cells except the pole (germ) cells. Two modes of DmcycE expression are observed in the subsequent divisions. During cycles 14, 15 and 16 in non-neural cells, DmcycE mRNA levels show no cell-cycle-associated variation. DmcycE expression in these cells is therefore independent of the cell cycle phase. In contrast, expression in proliferating embryonic peripheral nervous system cells occurs during interphase as a brief pulse that initiates before and overlaps with S phase, demonstrating the presence of a G1 phase in these embryonic neural cell cycles. DmcycE appears not to be expressed in cells that undergo endoreplication cycles during polytenization. The structural homology to human cyclin E, the ability of DmcycE to rescue a G1 cyclin-deficient yeast strain, the presence of multiple PEST sequences characteristic of G1-specific cyclins and expression during G1 phase in proliferating peripheral nervous system cells all argue that Drosophila cyclin E is a G1 cyclin. Constitutive DmcycE expression in embryonic cycles lacking a G1 phase, in contrast to expression during the G1-S phase transition in cycles exhibiting a G1 phase, implicates DmcycE expression in the regulation of the G1 to S phase transition during Drosophila embryogenesis.

Blood ◽  
2000 ◽  
Vol 96 (12) ◽  
pp. 3985-3987 ◽  
Author(s):  
Mu-Shui Dai ◽  
Charlie R. Mantel ◽  
Zhen-Biao Xia ◽  
Hal E. Broxmeyer ◽  
Li Lu

The dynamics of cell cycle regulation were investigated during in vitro erythroid proliferation and differentiation of CD34+cord blood cells. An unusual cell cycle profile with a majority of cells in S phase (70.2%) and minority of cells in G1 phase (27.4%) was observed in burst-forming unit-erythrocytes (BFU-E)–derived erythroblasts from a 7-day culture of CD34+ cells stimulated with interleukin 3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), Steel factor, and Epo. Terminal erythroid differentiation was accompanied by a rapid increase of G0/G1 phase cells. Expression of cyclin E and cyclin-dependent kinase 2 (cdk2) correlated with the proportion of S phase cells. Cyclin D3 was moderately up-regulated during the proliferation phase, and both cyclin E and D3 were rapidly down-regulated during terminal differentiation. This suggests that the high proliferation potential of erythroblasts is associated with temporal up-regulation of cyclin E and cdk2.


2005 ◽  
Vol 25 (14) ◽  
pp. 6140-6153 ◽  
Author(s):  
Angela Miele ◽  
Corey D. Braastad ◽  
William F. Holmes ◽  
Partha Mitra ◽  
Ricardo Medina ◽  
...  

ABSTRACT Genome replication in eukaryotic cells necessitates the stringent coupling of histone biosynthesis with the onset of DNA replication at the G1/S phase transition. A fundamental question is the mechanism that links the restriction (R) point late in G1 with histone gene expression at the onset of S phase. Here we demonstrate that HiNF-P, a transcriptional regulator of replication-dependent histone H4 genes, interacts directly with p220NPAT, a substrate of cyclin E/CDK2, to coactivate histone genes during S phase. HiNF-P and p220 are targeted to, and colocalize at, subnuclear foci (Cajal bodies) in a cell cycle-dependent manner. Genetic or biochemical disruption of the HiNF-P/p220 interaction compromises histone H4 gene activation at the G1/S phase transition and impedes cell cycle progression. Our results show that HiNF-P and p220 form a critical regulatory module that directly links histone H4 gene expression at the G1/S phase transition to the cyclin E/CDK2 signaling pathway at the R point.


2008 ◽  
Vol 415 (3) ◽  
pp. 439-448 ◽  
Author(s):  
Katherine A. Kaproth-Joslin ◽  
Xiangquan Li ◽  
Sarah E. Reks ◽  
Grant G. Kelley

In the present study, we examined the role of PLCδ1 (phospholipase C δ1) in the regulation of cellular proliferation. We demonstrate that RNAi (RNA interference)-mediated knockdown of endogenous PLCδ1, but not PLCβ3 or PLCϵ, induces a proliferation defect in Rat-1 and NIH 3T3 fibroblasts. The decreased proliferation was not due to an induction of apoptosis or senescence, but was associated with an approx. 60% inhibition of [3H]thymidine incorporation. Analysis of the cell cycle with BrdU (bromodeoxyuridine)/propidium iodide-labelled FACS (fluorescence-activated cell sorting) demonstrated an accumulation of cells in G0/G1-phase and a corresponding decrease in cells in S-phase. Further examination of the cell cycle after synchronization by serum-starvation demonstrated normal movement through G1-phase but delayed entry into S-phase. Consistent with these findings, G1 cyclin (D2 and D3) and CDK4 (cyclin-dependent kinase 4) levels and associated kinase activity were not affected. However, cyclin E-associated CDK2 activity, responsible for G1-to-S-phase progression, was inhibited. This decreased activity was accompanied by unchanged CDK2 protein levels and paradoxically elevated cyclin E and cyclin E-associated CDK2 levels, suggesting inhibition of the cyclin E–CDK2 complex. This inhibition was not due to altered stimulatory or inhibitory phosphorylation of CDK2. However, p27, a Cip/Kip family CKI (CDK inhibitor)-binding partner, was elevated and showed increased association with CDK2 in PLCδ1-knockdown cells. The result of the present study demonstrate a novel and critical role for PLCδ1 in cell-cycle progression from G1-to-S-phase through regulation of cyclin E–CDK2 activity and p27 levels.


Blood ◽  
1984 ◽  
Vol 63 (1) ◽  
pp. 105-113
Author(s):  
CW Distelhorst ◽  
BM Benutto ◽  
RA Bergamini

We determined the effect of cell cycle position on the amount of dexamethasone that was specifically bound by mouse and human lymphoid cell lines. Cell lines that were either sensitive or resistant to growth inhibition by dexamethasone were compared. Exponentially growing cells were separated by centrifugal elutriation into fractions that corresponded to different positions in the cell cycle. The cell cycle phase distribution of each fraction was estimated by flow cytometry and autoradiography. The amount of dexamethasone bound per cell in each fraction was measured by a whole cell binding assay. In three dexamethasone-sensitive cell lines (two mouse and one human), we found that the amount of dexamethasone bound per cell increased 2–4-fold between G1 phase and S phase, and then decreased during G2/M phase. Results were the same when the amount of dexamethasone bound per milligram of cell protein was measured. Binding affinity was the same during G1 phase and S phase, but the proportion of bound dexamethasone that translocated to the nucleus was greater during S phase. In contrast, we found that the amount of dexamethasone bound per cell by three dexamethasone-resistant cell lines (two mouse and one human) did not increase during S phase. Our results indicate that cell cycle changes in dexamethasone binding are not simply related to changes in cell protein or cell volume during the cell cycle. An increase in dexamethasone binding during S phase may be required for dexamethasone to inhibit cell growth, and a failure of dexamethasone binding to increase during S phase might represent a new mechanism of dexamethasone resistance in lymphoid cells.


Development ◽  
1998 ◽  
Vol 125 (24) ◽  
pp. 5069-5078 ◽  
Author(s):  
J. Horsfield ◽  
A. Penton ◽  
J. Secombe ◽  
F.M. Hoffman ◽  
H. Richardson

During eye development in Drosophila, cell cycle progression is coordinated with differentiation. Prior to differentiation, cells arrest in G1 phase anterior to and within the morphogenetic furrow. We show that Decapentaplegic (Dpp), a TGF-β family member, is required to establish this G1 arrest, since Dpp-unresponsive cells located in the anterior half of the morphogenetic furrow show ectopic S phases and ectopic expression of the cell cycle regulators Cyclins A, E and B. Conversely, ubiquitous over-expression of Dpp in the eye imaginal disc transiently inhibits S phase without affecting Cyclin E or Cyclin A abundance. This Dpp-mediated inhibition of S phase occurs independently of the Cyclin A inhibitor Roughex and of the expression of Dacapo, a Cyclin E-Cdk2 inhibitor. Furthermore, Dpp-signaling genes interact genetically with a hypomorphic cyclin E allele. Taken together our results suggest that Dpp acts to induce G1 arrest in the anterior part of the morphogenetic furrow by a novel inhibitory mechanism. In addition, our results provide evidence for a Dpp-independent mechanism that acts in the posterior part of the morphogenetic furrow to maintain G1 arrest.


Blood ◽  
1984 ◽  
Vol 63 (1) ◽  
pp. 105-113 ◽  
Author(s):  
CW Distelhorst ◽  
BM Benutto ◽  
RA Bergamini

Abstract We determined the effect of cell cycle position on the amount of dexamethasone that was specifically bound by mouse and human lymphoid cell lines. Cell lines that were either sensitive or resistant to growth inhibition by dexamethasone were compared. Exponentially growing cells were separated by centrifugal elutriation into fractions that corresponded to different positions in the cell cycle. The cell cycle phase distribution of each fraction was estimated by flow cytometry and autoradiography. The amount of dexamethasone bound per cell in each fraction was measured by a whole cell binding assay. In three dexamethasone-sensitive cell lines (two mouse and one human), we found that the amount of dexamethasone bound per cell increased 2–4-fold between G1 phase and S phase, and then decreased during G2/M phase. Results were the same when the amount of dexamethasone bound per milligram of cell protein was measured. Binding affinity was the same during G1 phase and S phase, but the proportion of bound dexamethasone that translocated to the nucleus was greater during S phase. In contrast, we found that the amount of dexamethasone bound per cell by three dexamethasone-resistant cell lines (two mouse and one human) did not increase during S phase. Our results indicate that cell cycle changes in dexamethasone binding are not simply related to changes in cell protein or cell volume during the cell cycle. An increase in dexamethasone binding during S phase may be required for dexamethasone to inhibit cell growth, and a failure of dexamethasone binding to increase during S phase might represent a new mechanism of dexamethasone resistance in lymphoid cells.


Development ◽  
1995 ◽  
Vol 121 (10) ◽  
pp. 3371-3379 ◽  
Author(s):  
H. Richardson ◽  
L.V. O'Keefe ◽  
T. Marty ◽  
R. Saint

During animal development, cell proliferation is controlled in many cases by regulation of the G1 to S phase transition. Studies of mammalian tissue culture cells have shown that the G1-specific cyclin, cyclin E, can be rate limiting for progression from G1 to S phase. During Drosophila development, down-regulation of cyclin E is required for G1 arrest in terminally differentiating embryonic epidermal cells. Whether cyclin E expression limits progression into S phase in proliferating, as opposed to differentiating, cells during development has not been investigated. Here we show that Drosophila cyclin E (DmcycE) protein is absent in G1 phase cells but appears at the onset of S phase in proliferating cells of the larval optic lobe and eye imaginal disc. We have examined cells in the eye imaginal epithelium, where a clearly defined developmentally regulated G1 to S phase transition occurs. Ectopic expression of DmcycE induces premature entry of most of these G1 cells into S phase. Thus in these cells, control of DmcycE expression is required for regulated entry into S phase. Significantly, a band of eye imaginal disc cells in G1 phase was not induced to enter S phase by ectopic expression of DmcycE. This provides evidence for additional regulatory mechanisms that operate during G1 phase to limit cell proliferation during development. These results demonstrate that the role of cyclin E in regulating progression into S phase in mammalian tissue culture cells applies to some, but not all, cells during Drosophila development.(ABSTRACT TRUNCATED AT 250 WORDS)


Blood ◽  
2000 ◽  
Vol 96 (12) ◽  
pp. 3985-3987 ◽  
Author(s):  
Mu-Shui Dai ◽  
Charlie R. Mantel ◽  
Zhen-Biao Xia ◽  
Hal E. Broxmeyer ◽  
Li Lu

Abstract The dynamics of cell cycle regulation were investigated during in vitro erythroid proliferation and differentiation of CD34+cord blood cells. An unusual cell cycle profile with a majority of cells in S phase (70.2%) and minority of cells in G1 phase (27.4%) was observed in burst-forming unit-erythrocytes (BFU-E)–derived erythroblasts from a 7-day culture of CD34+ cells stimulated with interleukin 3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), Steel factor, and Epo. Terminal erythroid differentiation was accompanied by a rapid increase of G0/G1 phase cells. Expression of cyclin E and cyclin-dependent kinase 2 (cdk2) correlated with the proportion of S phase cells. Cyclin D3 was moderately up-regulated during the proliferation phase, and both cyclin E and D3 were rapidly down-regulated during terminal differentiation. This suggests that the high proliferation potential of erythroblasts is associated with temporal up-regulation of cyclin E and cdk2.


1994 ◽  
Vol 14 (3) ◽  
pp. 1669-1679 ◽  
Author(s):  
D Resnitzky ◽  
M Gossen ◽  
H Bujard ◽  
S I Reed

Conditional overexpression of human cyclins B1, D1, and E was accomplished by using a synthetic cDNA expression system based on the Escherichia coli tetracycline repressor. After induction of these cyclins in asynchronous Rat-1 fibroblasts, a decrease in the length of the G1 interval was observed for cyclins D1 and E, consistent with an acceleration of the G1/S phase transition. We observed, in addition, a compensatory lengthening of S phase and G2 so that the mean cell cycle length in populations constitutively expressing these cyclins was unchanged relative to those of their uninduced counterparts. We found that expression of cyclin B1 had no effect on cell cycle dynamics, despite elevated levels of cyclin B-associated histone H1 kinase activity. Induction of cyclins D1 and E also accelerated entry into S phase for synchronized cultures emerging from quiescence. However, whereas cyclin E exerted a greater effect than cyclin D1 in asynchronous cycling cells, cyclin D1 conferred a greater effect upon stimulation from quiescence, suggesting a specific role for cyclin D1 in the G0-to-G1 transition. Overexpression of cyclins did not prevent cells from entering into quiescence upon serum starvation, although a slight delay in attainment of quiescence was observed for cells expressing either cyclin D1 or cyclin E. These results suggest that cyclins D1 and E are rate-limiting activators of the G1-to-S phase transition and that cyclin D1 might play a specialized role in facilitating emergence from quiescence.


Development ◽  
2000 ◽  
Vol 127 (21) ◽  
pp. 4619-4630 ◽  
Author(s):  
L. Jones ◽  
H. Richardson ◽  
R. Saint

Cyclin E is an essential regulator of S phase entry. We have previously shown that transcriptional regulation of the gene that encodes Drosophila cyclin E, DmcycE, plays an important role in the control of the G(1) to S phase transition during development. We report here the first comprehensive analysis of the transcriptional regulation of a G(1)phase cell cycle regulatory gene during embryogenesis. Analysis of deficiencies, a genomic transformant and reporter gene constructs revealed that DmcycE transcription is controlled by a large and complex cis-regulatory region containing tissue- and stage-specific components. Separate regulatory elements for transcription in epidermal cells during cell cycles 14–16, central nervous system cells and peripheral nervous system cells were found. An additional cis-regulatory element drives transcription in thoracic epidermal cells that undergo a 17th cell cycle when other epidermal cells have arrested in G(1)phase prior to terminal differentiation. The complexity of DmcycE transcriptional regulation argues against a model in which DmcycE transcription is regulated simply and solely by G(1) to S phase transcription regulators such as RB, E2F and DP. Rather, our study demonstrates that tissue-specific transcriptional regulatory mechanisms are important components of the control of cyclin E transcription and thus of cell proliferation in metazoans.


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