scholarly journals SCAPER, a novel cyclin A–interacting protein that regulates cell cycle progression

2007 ◽  
Vol 178 (4) ◽  
pp. 621-633 ◽  
Author(s):  
William Y. Tsang ◽  
Leyu Wang ◽  
Zhihong Chen ◽  
Irma Sánchez ◽  
Brian David Dynlacht
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Regulatory Protein ◽  
Ectopic Expression ◽  
Cyclin A ◽  
Eukaryotic Cell ◽  
S Phase ◽  
Interacting Protein ◽  
M Phase

Cyclin A/Cdk2 plays an important role during S and G2/M phases of the eukaryotic cell cycle, but the mechanisms by which it regulates cell cycle events are not fully understood. We have biochemically purified and identified SCAPER, a novel protein that specifically interacts with cyclin A/Cdk2 in vivo. Its expression is cell cycle independent, and it associates with cyclin A/Cdk2 at multiple phases of the cell cycle. SCAPER localizes primarily to the endoplasmic reticulum. Ectopic expression of SCAPER sequesters cyclin A from the nucleus and results specifically in an accumulation of cells in M phase of the cell cycle. RNAi-mediated depletion of SCAPER decreases the cytoplasmic pool of cyclin A and delays the G1/S phase transition upon cell cycle re-entry from quiescence. We propose that SCAPER represents a novel cyclin A/Cdk2 regulatory protein that transiently maintains this kinase in the cytoplasm. SCAPER could play a role in distinguishing S phase– from M phase–specific functions of cyclin A/Cdk2.

scholarly journals Control of cell cycle progression by phosphorylation of cyclin-dependent kinase (CDK) substrates

2010 ◽  
Vol 30 (4) ◽  
pp. 243-255 ◽  
Author(s):  
Randy Suryadinata ◽  
Martin Sadowski ◽  
Boris Sarcevic
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Cycle Progression ◽  
Genetic Material ◽  
Eukaryotic Cell ◽  
S Phase ◽  
Cycle Progression ◽  
M Phase ◽  
Unicellular Organisms ◽  
Multicellular Organisms

The eukaryotic cell cycle is a fundamental evolutionarily conserved process that regulates cell division from simple unicellular organisms, such as yeast, through to higher multicellular organisms, such as humans. The cell cycle comprises several phases, including the S-phase (DNA synthesis phase) and M-phase (mitotic phase). During S-phase, the genetic material is replicated, and is then segregated into two identical daughter cells following mitotic M-phase and cytokinesis. The S- and M-phases are separated by two gap phases (G1 and G2) that govern the readiness of cells to enter S- or M-phase. Genetic and biochemical studies demonstrate that cell division in eukaryotes is mediated by CDKs (cyclin-dependent kinases). Active CDKs comprise a protein kinase subunit whose catalytic activity is dependent on association with a regulatory cyclin subunit. Cell-cycle-stage-dependent accumulation and proteolytic degradation of different cyclin subunits regulates their association with CDKs to control different stages of cell division. CDKs promote cell cycle progression by phosphorylating critical downstream substrates to alter their activity. Here, we will review some of the well-characterized CDK substrates to provide mechanistic insights into how these kinases control different stages of cell division.

scholarly journals Candida albicans Cyclin Clb4 Carries S-Phase Cyclin Activity

2010 ◽  
Vol 9 (9) ◽  
pp. 1311-1319 ◽  
Author(s):  
Ayala Ofir ◽  
Daniel Kornitzer
Keyword(s):  
Cell Cycle ◽  
Candida Albicans ◽  
Cell Cycle Progression ◽  
Sequence Similarity ◽  
Eukaryotic Cell ◽  
S Phase ◽  
Pathogenic Yeast ◽  
Content Type

ABSTRACT Cyclin-dependent kinases (CDKs) are key regulators of eukaryotic cell cycle progression. The cyclin subunit activates the CDK and also imparts to the complex, at least in some cases, substrate specificity. Saccharomyces cerevisiae, an organism in which the roles of individual cyclins are best studied, contains nine cyclins (three G1 cyclins and six B-type cyclins) capable of activating the main cell cycle CDK, Cdc28. Analysis of the genome of the pathogenic yeast Candida albicans revealed only two sequences corresponding to B-type cyclins, C. albicans Clb2 (CaClb2) and CaClb4. Notably, no homolog of the S. cerevisiae S-phase-specific cyclins, Clb5/Clb6, could be detected. Here, we performed an in vitro analysis of the activity of CaClb2 and CaClb4 and of three G1 cyclins, as well as an analysis of the phenotype of S. cerevisiae cells expressing CaClb2 or CaClb4 instead of Clb5. Remarkably, replacement of CLB5 by CaCLB4 caused rapid diploidization of S. cerevisiae. In addition, both in vivo and in vitro analyses indicate that, in spite of the higher sequence similarity of CaClb2 to Clb5/Clb6, CaClb4 is the functional homolog of Clb5/Clb6. The activity of a CaClb2/CaClb4 cyclin hybrid suggests that the cyclin box domain of CaClb4 carries the functional specificity of the protein. These results have implications for our understanding of the evolution of specificity of the cell cycle cyclins.

scholarly journals HIRA, the Human Homologue of Yeast Hir1p and Hir2p, Is a Novel Cyclin-cdk2 Substrate Whose Expression Blocks S-Phase Progression

2001 ◽  
Vol 21 (5) ◽  
pp. 1854-1865 ◽  
Author(s):  
Caitlin Hall ◽  
David M. Nelson ◽  
Xiaofen Ye ◽  
Kayla Baker ◽  
James A. DeCaprio ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Ectopic Expression ◽  
Cyclin A ◽  
S Phase ◽  
Dependent Manner ◽  
Sequence Motifs ◽  
Histone Gene Expression ◽  
Phase Progression

ABSTRACT Substrates of cyclin-cdk2 kinases contain two distinct primary sequence motifs: a cyclin-binding RXL motif and one or more phosphoacceptor sites (consensus S/TPXK/R or S/TP). To identify novel cyclin-cdk2 substrates, we searched the database for proteins containing both of these motifs. One such protein is human HIRA, the homologue of two cell cycle-regulated repressors of histone gene expression in Saccharomyces cerevisiae, Hir1p and Hir2p. Here we demonstrate that human HIRA is an in vivo substrate of a cyclin-cdk2 kinase. First, HIRA bound to and was phosphorylated by cyclin A- and E-cdk2 in vitro in an RXL-dependent manner. Second, HIRA was phosphorylated in vivo on two consensus cyclin-cdk2 phosphoacceptor sites and at least one of these, threonine 555, was phosphorylated by cyclin A-cdk2 in vitro. Third, phosphorylation of HIRA in vivo was blocked by cyclin-cdk2 inhibitor p21cip1. Fourth, HIRA became phosphorylated on threonine 555 in S phase when cyclin-cdk2 kinases are active. Fifth, HIRA was localized preferentially to the nucleus, where active cyclin A- and E-cdk2 are located. Finally, ectopic expression of HIRA in cells caused arrest in S phase and this is consistent with the notion that it is a cyclin-cdk2 substrate that has a role in control of the cell cycle.

scholarly journals The Paramyxovirus Simian Virus 5 V Protein Slows Progression of the Cell Cycle

2000 ◽  
Vol 74 (19) ◽  
pp. 9152-9166 ◽  
Author(s):  
Grace Y. Lin ◽  
Robert A. Lamb
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Simian Virus ◽  
S Phase ◽  
V Protein ◽  
Simian Virus 5 ◽  
C Terminus ◽  
M Phase ◽  
Infected Cells ◽  
Affect Cell Cycle Progression

ABSTRACT Infection of cells by many viruses affects the cell division cycle of the host cell to favor viral replication. We examined the ability of the paramyxovirus simian parainfluenza virus 5 (SV5) to affect cell cycle progression, and we found that SV5 slows the rate of proliferation of HeLa T4 cells. The SV5-infected cells had a delayed transition from G1 to S phase and prolonged progression through S phase, and some of the infected cells were arrested in G2 or M phase. The levels of p53 and p21CIP1were not increased in SV5-infected cells compared to mock-infected cells, suggesting that the changes in the cell cycle occur through a p53-independent mechanism. However, the phosphorylation of the retinoblastoma protein (pRB) was delayed and prolonged in SV5-infected cells. The changes in the cell cycle were also observed in cells expressing the SV5 V protein but not in the cells expressing the SV5 P protein or the V protein lacking its unique C terminus (VΔC). The unique C terminus of the V protein of SV5 was shown previously to interact with DDB1, which is the 127-kDa subunit of the multifunctional damage-specific DNA-binding protein (DDB) heterodimer. The coexpression of DDB1 with V can partially restore the changes in the cell cycle caused by expression of the V protein.

scholarly journals Identification of HiNF-P, a Key Activator of Cell Cycle-Controlled Histone H4 Genes at the Onset of S Phase

2003 ◽  
Vol 23 (22) ◽  
pp. 8110-8123 ◽  
Author(s):  
Partha Mitra ◽  
Rong-Lin Xie ◽  
Ricardo Medina ◽  
Hayk Hovhannisyan ◽  
S. Kaleem Zaidi ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Cyclin E ◽  
S Phase ◽  
Phase Cell ◽  
Regulatory Sequences ◽  
Histone H4 ◽  
Restriction Point ◽  
Histone H4 Gene

ABSTRACT At the G1/S phase cell cycle transition, multiple histone genes are expressed to ensure that newly synthesized DNA is immediately packaged as chromatin. Here we have purified and functionally characterized the critical transcription factor HiNF-P, which is required for E2F-independent activation of the histone H4 multigene family. Using chromatin immunoprecipitation analysis and ligation-mediated PCR-assisted genomic sequencing, we show that HiNF-P interacts with conserved H4 cell cycle regulatory sequences in vivo. Antisense inhibition of HiNF-P reduces endogenous histone H4 gene expression. Furthermore, we find that HiNF-P utilizes NPAT/p220, a substrate of the cyclin E/cyclin-dependent kinase 2 (CDK2) kinase complex, as a key coactivator to enhance histone H4 gene transcription. The biological role of HiNF-P is reflected by impeded cell cycle progression into S phase upon antisense-mediated reduction of HiNF-P levels. Our results establish that HiNF-P is the ultimate link in a linear signaling pathway that is initiated with the growth factor-dependent induction of cyclin E/CDK2 kinase activity at the restriction point and culminates in the activation of histone H4 genes through HiNF-P at the G1/S phase transition.

scholarly journals BRCA1 Is Phosphorylated at Serine 1497 In Vivo at a Cyclin-Dependent Kinase 2 Phosphorylation Site

1999 ◽  
Vol 19 (7) ◽  
pp. 4843-4854 ◽  
Author(s):  
Heinz Ruffner ◽  
Wei Jiang ◽  
A. Grey Craig ◽  
Tony Hunter ◽  
Inder M. Verma
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Phosphorylation Site ◽  
Cyclin A ◽  
Dominant Negative ◽  
Protein Kinase Activity ◽  
Cyclin Dependent Kinase

ABSTRACT BRCA1 is a cell cycle-regulated nuclear protein that is phosphorylated mainly on serine and to a lesser extent on threonine residues. Changes in phosphorylation occur in response to cell cycle progression and DNA damage. Specifically, BRCA1 undergoes hyperphosphorylation during late G1 and S phases of the cell cycle. Here we report that BRCA1 is phosphorylated in vivo at serine 1497 (S1497), which is part of a cyclin-dependent kinase (CDK) consensus site. S1497 can be phosphorylated in vitro by CDK2-cyclin A or E. BRCA1 coimmunoprecipitates with an endogenous serine-threonine protein kinase activity that phosphorylates S1497 in vitro. This cellular kinase activity is sensitive to transfection of a dominant negative form of CDK2 as well as the application of the CDK inhibitors p21 and butyrolactone I but not p16. Furthermore, BRCA1 coimmunoprecipitates with CDK2 and cyclin A. These results suggest that the endogenous kinase activity is composed of CDK2-cyclin complexes, at least in part, concordant with the G1/S-specific increase in BRCA1 phosphorylation.

scholarly journals Cdc53p acts in concert with Cdc4p and Cdc34p to control the G1-to-S-phase transition and identifies a conserved family of proteins.

1996 ◽  
Vol 16 (12) ◽  
pp. 6634-6643 ◽  
Author(s):  
N Mathias ◽  
S L Johnson ◽  
M Winey ◽  
A E Adams ◽  
L Goetsch ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Large Family ◽  
S Phase ◽  
Genetic Interactions ◽  
Cycle Progression ◽  
Cyclin Dependent Kinases ◽  
Ubiquitin Conjugating Enzyme ◽  
Regulation Of Cell Cycle

Regulation of cell cycle progression occurs in part through the targeted degradation of both activating and inhibitory subunits of the cyclin-dependent kinases. During G1, CDC4, encoding a WD-40 repeat protein, and CDC34, encoding a ubiquitin-conjugating enzyme, are involved in the destruction of these regulators. Here we describe evidence indicating that CDC53 also is involved in this process. Mutations in CDC53 cause a phenotype indistinguishable from those of cdc4 and cdc34 mutations, numerous genetic interactions are seen between these genes, and the encoded proteins are found physically associated in vivo. Cdc53p defines a large family of proteins found in yeasts, nematodes, and humans whose molecular functions are uncharacterized. These results suggest a role for this family of proteins in regulating cell cycle proliferation through protein degradation.

scholarly journals Cyclin A expression is under negative transcriptional control during the cell cycle.

1996 ◽  
Vol 16 (7) ◽  
pp. 3789-3798 ◽  
Author(s):  
X Huet ◽  
J Rech ◽  
A Plet ◽  
A Vié ◽  
J M Blanchard
Keyword(s):  
Cell Cycle ◽  
Transcriptional Repression ◽  
Transcriptional Control ◽  
Cell Cycle Progression ◽  
Cyclin A ◽  
Luciferase Reporter ◽  
Luciferase Reporter Gene ◽  
Proliferating Cells

Transcription of the gene coding for cyclin A, a protein required for S-phase transit, is cell cycle regulated and is restricted to proliferating cells. To further explore transcriptional regulation linked to cell division cycle control, a genomic clone containing 5' flanking sequences of the murine cyclin A gene was isolated. When it was fused to a luciferase reporter gene, it was shown to function as a proliferation-regulated promoter in NIH 3T3 cells. Transcription of the mouse cyclin A gene is negatively regulated by arrest of cell proliferation. A mutation of a GC-rich sequence conserved between mice and humans is sufficient to relieve transcriptional repression, resulting in a promoter with constitutively high activity. In agreement with this result, in vivo footprinting reveals a protection of the cell cycle-responsive element in G0/early G1 cells which is not observed at later stages of the cell cycle. Moreover, the footprint is present in dimethyl sulfoxide-induced differentiating and not in proliferating Friend erythroleukemia cells. Conversely, two other sites, which in vitro bind ATF-1 and NF-Y, respectively, are constitutively occupied throughout cell cycle progression.

scholarly journals BCL-2 Is Phosphorylated and Inactivated by an ASK1/Jun N-Terminal Protein Kinase Pathway Normally Activated at G2/M

1999 ◽  
Vol 19 (12) ◽  
pp. 8469-8478 ◽  
Author(s):  
Kazuhito Yamamoto ◽  
Hidenori Ichijo ◽  
Stanley J. Korsmeyer
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Cell Cycle Progression ◽  
Peptide Mapping ◽  
Dominant Negative ◽  
Terminal Protein ◽  
Cycle Progression ◽  
M Phase ◽  
Death Signals

ABSTRACT Multiple signal transduction pathways are capable of modifying BCL-2 family members to reset susceptibility to apoptosis. We used two-dimensional peptide mapping and sequencing to identify three residues (Ser70, Ser87, and Thr69) within the unstructured loop of BCL-2 that were phosphorylated in response to microtubule-damaging agents, which also arrest cells at G2/M. Changing these sites to alanine conferred more antiapoptotic activity on BCL-2 following physiologic death signals as well as paclitaxel, indicating that phosphorylation is inactivating. An examination of cycling cells enriched by elutriation for distinct phases of the cell cycle revealed that BCL-2 was phosphorylated at the G2/M phase of the cell cycle. G2/M-phase cells proved more susceptible to death signals, and phosphorylation of BCL-2 appeared to be responsible, as a Ser70Ala substitution restored resistance to apoptosis. We noted that ASK1 and JNK1 were normally activated at G2/M phase, and JNK was capable of phosphorylating BCL-2. Expression of a series of wild-type and dominant-negative kinases indicated an ASK1/Jun N-terminal protein kinase 1 (JNK1) pathway phosphorylated BCL-2 in vivo. Moreover, the combination of dominant negative ASK1, (dnASK1), dnMKK7, and dnJNK1 inhibited paclitaxel-induced BCL-2 phosphorylation. Thus, stress response kinases phosphorylate BCL-2 during cell cycle progression as a normal physiologic process to inactivate BCL-2 at G2/M.

scholarly journals Cell cycle regulation of cyclin A gene expression by the cyclic AMP-responsive transcription factors CREB and CREM.

1995 ◽  
Vol 15 (6) ◽  
pp. 3301-3309 ◽  
Author(s):  
C Desdouets ◽  
G Matesic ◽  
C A Molina ◽  
N S Foulkes ◽  
P Sassone-Corsi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Cyclic Amp ◽  
Transcription Initiation ◽  
Mammalian Cells ◽  
Binding Proteins ◽  
Regulatory Protein ◽  
Cyclin A ◽  
S Phase ◽  
Signalling Pathway

Cyclin A is a pivotal regulatory protein which, in mammalian cells, is involved in the S phase of the cell cycle. Transcription of the human cyclin A gene is cell cycle regulated. We have investigated the role of the cyclic AMP (cAMP)-dependent signalling pathway in this cell cycle-dependent control. In human diploid fibroblasts (Hs 27), induction of cyclin A gene expression at G1/S is stimulated by 8-bromo-cAMP and suppressed by the protein kinase A inhibitor H89, which was found to delay S phase entry. Transfection experiments showed that the cyclin A promoter is inducible by activation of the adenylyl cyclase signalling pathway. Stimulation is mediated predominantly via a cAMP response element (CRE) located at positions -80 to -73 with respect to the transcription initiation site and is able to bind CRE-binding proteins and CRE modulators. Moreover, activation by phosphorylation of the activators CRE-binding proteins and CRE modulator tau and levels of the inducible cAMP early repressor are cell cycle regulated, which is consistent with the pattern of cyclin A inducibility by cAMP during the cell cycle. These results suggest that the CRE is, at least partly, implicated in stimulation of cyclin A transcription at G1/S.

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