A mutant E2F-1 transcription factor that affects the phenotype of NIH3T3 fibroblasts inefficiently associates with cyclin A - cdk2

1998 ◽  
Vol 76 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Kelly L Jordan-Sciutto ◽  
David J Hall
Keyword(s):  
Cell Cycle ◽  
Amino Acids ◽  
Transcription Factor ◽  
Cyclin A ◽  
Chemotherapeutic Agents ◽  
S Phase ◽  
Full Length ◽  
Vitro Assay ◽  
Amino Terminal

The amino-terminal domain of the E2F1 transcription factor is the site of association with cyclin A - cdk2, mapping to residues 87-94. A mutant of E2F1 lacking the first 87 amino acids (termed E2F1d87) has a number of potent effects on cellular phenotype when constitutively expressed in NIH3T3 fibroblasts. For example, in these fibroblasts the duration of S phase and the sensitivity to S phase chemotherapeutic agents are both increased. Since E2F1d87 only partially truncates the cyclin A - cdk2 binding domain, it was important to determine the level of cyclin A - cdk2 association with this mutant to correlate any reduction in association with the observed effects on the cell cycle. It was found that cyclin A - cdk2 binds E2F1d87 in an in vitro assay but that this binding is reduced approximately 8 fold compared with binding to full-length E2F1, whereas no detectable binding was seen to a mutant E2F1 that lacks the first 117 amino acids. Correspondingly, H1 kinase activity in E2F1d87 immunoprecipitates from E2F1d87-expressing cells was significantly reduced compared with that seen for full-length E2F1. From these data it appears that E2F1 with reduced cyclin A - cdk2 binding activity mediates the alteration in cell cycle parameters seen in these cells.Key words: E2F1, apoptosis, cyclin A, cell cycle.

scholarly journals p130 and p107 use a conserved domain to inhibit cellular cyclin-dependent kinase activity.

1997 ◽  
Vol 17 (7) ◽  
pp. 3566-3579 ◽  
Author(s):  
M S Woo ◽  
I Sánchez ◽  
B D Dynlacht
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Kinase Activity ◽  
Cyclin E ◽  
Critical Role ◽  
Cyclin A ◽  
Terminal Region ◽  
Cyclin Dependent Kinase ◽  
Amino Terminal

The pRB-related proteins p107 and p130 are thought to suppress growth in part through their associations with two important cell cycle kinases, cyclin A-cdk2 and cyclin E-cdk2, and transcription factor E2F. Although each protein plays a critical role in cell proliferation, the functional consequences of the association among growth suppressor, cyclin-dependent kinase, and transcription factor have remained elusive. In an attempt to understand the biochemical properties of such complexes, we reconstituted each of the p130-cyclin-cdk2 and p107-cyclin-cdk2 complexes found in vivo with purified, recombinant proteins. Strikingly, stoichiometric association of p107 or p130 with either cyclin E-cdk2 or cyclin A-cdk2 negated the activities of these kinases. The results of our experiments suggest that inhibition does not result from substrate competition or loss of cdk2 activation. Kinase inhibitory activity was dependent upon an amino-terminal region of p107 that is highly conserved with p130. Further, a role for this amino-terminal region in growth suppression was uncovered by using p107 mutants unable to bind E2F. To determine whether cellular complexes might display similar regulatory properties, we purified p130-cyclin A-cdk2 complexes from human cells and found that such complexes exist in two forms, one that contains E2F-4-DP-1 and one that lacks the heterodimer. These endogenous complexes behaved like the in vitro-reconstituted complexes, exhibiting low levels of associated kinase activity that could be significantly augmented by dissociation of p130. The results of these experiments suggest a mechanism whereby p130 and p107 suppress growth by inhibiting important cell cycle kinases.

scholarly journals A Cyclin-Binding Motif within the Amino-Terminal Homology Domain of EBNA3C Binds Cyclin A and Modulates Cyclin A-Dependent Kinase Activity in Epstein-Barr Virus-Infected Cells

2004 ◽  
Vol 78 (23) ◽  
pp. 12857-12867 ◽  
Author(s):  
Jason S. Knight ◽  
Nikhil Sharma ◽  
Danielle E. Kalman ◽  
Erle S. Robertson
Keyword(s):  
Amino Acids ◽  
Epstein Barr Virus ◽  
Kinase Activity ◽  
Cyclin A ◽  
Carboxy Terminus ◽  
Barr Virus ◽  
Amino Terminal ◽  
Infected Cells ◽  
Epstein Barr

ABSTRACT The Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA3C) is a virus-encoded latent antigen essential for primary B-cell transformation. In this report we demonstrate that although the carboxy terminus of EBNA3C predominantly regulates cyclin A-dependent kinase activity, the region of greatest affinity for cyclin A lies within the EBNA3 amino-terminal homology domain of EBNA3C. Detailed mapping studies employing both in vitro binding assays and coimmunoprecipitation experiments implicated a small region of EBNA3C, amino acids 130 to 159 within the EBNA3 homology domain, as having the greatest affinity for cyclin A. The EBNA3 homology domain has the highest degree of amino acid similarity (approximately 30%) between the EBNA3 proteins, and, indeed, EBNA3B, but not EBNA3A, showed binding activity with cyclin A. We also show that EBNA3C binds to the α1 helix of the highly conserved mammalian cyclin box, with cyclin A amino acids 206 to 226 required for strong binding to EBNA3C amino acids 130 to 159. Interestingly, EBNA3C also bound human cyclins D1 and E in vitro, although the affinity was approximately 30% of that seen for cyclin A. Previously it was demonstrated that full-length EBNA3C rescues p27-mediated suppression of cyclin A-dependent kinase activity (J. S. Knight and E. S. Robertson, J. Virol. 78:1981-1991, 2004). It was also demonstrated that the carboxy terminus of EBNA3C recapitulates this phenotype. Surprisingly, the amino terminus of EBNA3C with the highest affinity for cyclin A was unable to rescue p27 suppression of kinase activity and actually downregulates cyclin A activity when introduced into EBV-infected cells. The data presented here suggests that the amino terminus of EBNA3C may play an important role in recruiting cyclin A complexes, while the carboxy terminus of EBNA3C is necessary for the functional modulation of cyclin A complex kinase activity.

Isolation and characterization of full-length functional cDNA clones for human carcinoembryonic antigen

1987 ◽  
Vol 7 (9) ◽  
pp. 3221-3230
Author(s):  
N Beauchemin ◽  
S Benchimol ◽  
D Cournoyer ◽  
A Fuks ◽  
C P Stanners
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Amino Acid ◽  
Carcinoembryonic Antigen ◽  
Full Length ◽  
Cdna Clones ◽  
Base Pairs ◽  
Amino Terminal ◽  
Isolation And Characterization

Carcinoembryonic antigen (CEA) expression is perhaps the most prevalent of phenotypic changes observed in human cancer cells. The molecular genetic basis of this phenomenon, however, is completely unknown. Twenty-seven CEA cDNA clones were isolated from a human colon adenocarcinoma cell line. Most of these clones are full length and consist of a number (usually three) of surprisingly similar long (534 base pairs) repeats between a 5' end of 520 base pairs and a 3' end with three different termination points. The predicted translation product of these clones consists of a processed signal sequence of 34 amino acids, an amino-terminal sequence of 107 amino acids, which includes the known terminal amino acid sequence of CEA, three repeated domains of 178 amino acids each, and a membrane-anchoring domain of 27 amino acids, giving a total of 702 amino acids and a molecular weight of 72,813 for the mature protein. The repeated domains have conserved features, including the first 67 amino acids at their N termini and the presence of four cysteine residues. Comparisons with the amino acid sequences of other proteins reveals homology of the repeats with various members of the immunoglobulin supergene family, particularly the human T-cell receptor gamma chain. CEA cDNA clones in the SP-65 vector were shown to produce transcripts in vitro which could be translated in vitro to yield a protein of molecular weight 73,000 which in turn could be precipitated with CEA-specific antibodies. CEA cDNA clones were also inserted into an animal cell expression vector and introduced by transfection into mammalian cell lines. These transfectants produced a CEA-immunoprecipitable glycoprotein which could be visualized by immunofluorescence on the cell surface.

scholarly journals Isolation and characterization of full-length functional cDNA clones for human carcinoembryonic antigen.

1987 ◽  
Vol 7 (9) ◽  
pp. 3221-3230 ◽  
Author(s):  
N Beauchemin ◽  
S Benchimol ◽  
D Cournoyer ◽  
A Fuks ◽  
C P Stanners
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Amino Acid ◽  
Carcinoembryonic Antigen ◽  
Full Length ◽  
Cdna Clones ◽  
Base Pairs ◽  
Amino Terminal ◽  
Isolation And Characterization

Carcinoembryonic antigen (CEA) expression is perhaps the most prevalent of phenotypic changes observed in human cancer cells. The molecular genetic basis of this phenomenon, however, is completely unknown. Twenty-seven CEA cDNA clones were isolated from a human colon adenocarcinoma cell line. Most of these clones are full length and consist of a number (usually three) of surprisingly similar long (534 base pairs) repeats between a 5' end of 520 base pairs and a 3' end with three different termination points. The predicted translation product of these clones consists of a processed signal sequence of 34 amino acids, an amino-terminal sequence of 107 amino acids, which includes the known terminal amino acid sequence of CEA, three repeated domains of 178 amino acids each, and a membrane-anchoring domain of 27 amino acids, giving a total of 702 amino acids and a molecular weight of 72,813 for the mature protein. The repeated domains have conserved features, including the first 67 amino acids at their N termini and the presence of four cysteine residues. Comparisons with the amino acid sequences of other proteins reveals homology of the repeats with various members of the immunoglobulin supergene family, particularly the human T-cell receptor gamma chain. CEA cDNA clones in the SP-65 vector were shown to produce transcripts in vitro which could be translated in vitro to yield a protein of molecular weight 73,000 which in turn could be precipitated with CEA-specific antibodies. CEA cDNA clones were also inserted into an animal cell expression vector and introduced by transfection into mammalian cell lines. These transfectants produced a CEA-immunoprecipitable glycoprotein which could be visualized by immunofluorescence on the cell surface.

scholarly journals Phosphorylation of Threonine 61 by Cyclin A/Cdk1 Triggers Degradation of Stem-Loop Binding Protein at the End of S Phase

2008 ◽  
Vol 28 (14) ◽  
pp. 4469-4479 ◽  
Author(s):  
M. Murat Koseoglu ◽  
Lee M. Graves ◽  
William F. Marzluff
Keyword(s):  
Cell Cycle ◽  
Fusion Proteins ◽  
Regulatory Mechanism ◽  
Binding Protein ◽  
Cyclin A ◽  
S Phase ◽  
Mrna Levels ◽  
Histone Mrna ◽  
Stem Loop

ABSTRACT Histone mRNA levels are cell cycle regulated, and a major regulatory mechanism is restriction of stem-loop binding protein (SLBP) to S phase. Degradation of SLBP at the end of S phase results in cessation of histone mRNA biosynthesis, preventing accumulation of histone mRNA until SLBP is synthesized just before entry into the next S phase. Degradation of SLBP requires an SFTTP (58 to 62) and KRKL (95 to 98) sequence, which is a putative cyclin binding site. A fusion protein with the 58-amino-acid sequence of SLBP (amino acids 51 to 108) fused to glutathione S-transferase (GST) is sufficient to mimic SLBP degradation at late S phase. Using GST-SLBP fusion proteins as a substrate, we show that cyclin A/Cdk1 phosphorylates Thr61. Furthermore, knockdown of Cdk1 by RNA interference stabilizes SLBP at the end of S phase. Phosphorylation of Thr61 is necessary for subsequent phosphorylation of Thr60 by CK2 in vitro. Inhibitors of CK2 also prevent degradation of SLBP at the end of S phase. Thus, phosphorylation of Thr61 by cyclin A/Cdk1 primes phosphorylation of Thr60 by CK2 and is responsible for initiating SLBP degradation. We conclude that the increase in cyclin A/Cdk1 activity at the end of S phase triggers degradation of SLBP at S/G2.

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 Activation of the p34 CDC2 protein kinase at the start of S phase in the human cell cycle.

1992 ◽  
Vol 3 (4) ◽  
pp. 389-401 ◽  
Author(s):  
R L Marraccino ◽  
E J Firpo ◽  
J M Roberts
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Cyclin A ◽  
S Phase ◽  
Cdc2 Kinase ◽  
G1 Cells ◽  
Sv40 Dna ◽  
P34 Cdc2

Using a protocol for selecting cells on the basis of both size and age (with respect to the preceding mitosis), we isolated highly synchronous human G1 cells. With this procedure, we demonstrated that the p34 CDC2 kinase was activated at the start of S phase. Cyclin A synthesis began at the same time, and activation of the p34 CDC2 kinase at the start of S phase was, at least in part, due to its association with cyclin A. Furthermore, cells synchronized in late G1 by exposure to the drug mimosine contain active cyclin A/p34 CDC2 kinase, indicating that p34 CDC2 activation can occur before DNA synthesis begins. Thus, the cyclin A/CDC2 complex, which previously has been shown to be sufficient to start SV40 DNA synthesis in vitro, assembles and is activated at the start of S phase in vivo.

scholarly journals The role of E26 transformation-specific variant transcription factor 5 in colorectal cancer cell proliferation and cell cycle progression

2021 ◽  
Vol 12 (5) ◽  
Author(s):  
Yi Peng ◽  
Haoran Feng ◽  
Changgang Wang ◽  
Zijia Song ◽  
Yaqi Zhang ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Cell Cycle ◽  
Transcription Factor ◽  
Tumor Growth ◽  
Drug Sensitivity ◽  
Phase Transfer ◽  
S Phase ◽  
Luciferase Reporter ◽  
P21 Promoter

AbstractE26 transformation-specific variant transcription factor 5 (ETV5) contributes to tumor growth and progression and promotes colorectal cancer (CRC) angiogenesis. Previous studies indicate that ETV5 may regulate the cell cycle, but its detailed mechanism remain unclear. Gene Ontology (GO) analysis of RNA-seq data revealed that ETV5 possibly regulates the cell cycle in CRC. Here, in vitro and in vivo experiments were performed to verify that ETV5 promoted tumor progression and influenced cell cycle G1/S transition. Cell cycle PCR array and co-immunoprecipitation (Co-IP) helped identify the p21-CDKs pathway. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays were performed to determine whether ETV5 binds to the p21 promoter. ETV5 and p21 were detected by immunohistochemistry, and the effects of their expression on CRC patients were evaluated. ETV5 upregulation enhanced tumor proliferative capacity and promoted G1 phase transfer to the S phase. ETV5 knockdown slowed the growth of CRC cells and repressed the G1/S transition. We also found p21 as a downstream target of ETV5. p21 knockdown resulted in faster CRC cell growth and in more cells being driven from the G0/1 phase into the S phase. Co-IP experiments showed that p21 banding to CDK2, CDK4, and CDK6 inhibited p130 phosphorylation. Using the ChIP and luciferase reporter assay, we confirmed that ETV5 bound to the p21 promoter and repressed p21 expression. CRC patients with high ETV5 expression and low p21 expression showed the worst prognosis. Finally, by targeting p21 to regulate CDK function, ETV5 also changed drug-sensitivity to palbociclib and dinaciclib. In conclusion, ETV5 promoted cell cycle G1/S transition through transcriptional inhibition of p21, thereby accelerating tumor growth. Moreover, ETV5 changed drug-sensitivity to palbociclib and dinaciclib. Therefore, therapeutic regimens targeting ETV5 may be promising in improving the efficacy of target-CDK treatment in CRC.

In vitro evidence that LHRH stimulates the recruitment of prolactin mRNA-expressing cells during the postnatal period in the rat

1994 ◽  
Vol 12 (1) ◽  
pp. 107-118 ◽  
Author(s):  
A Van Bael ◽  
R Huygen ◽  
B Himpens ◽  
C Denef
Keyword(s):  
Cell Cycle ◽  
Cell Population ◽  
Blot Hybridization ◽  
Postnatal Period ◽  
S Phase ◽  
Female Rats ◽  
Mrna Levels ◽  
Dot Blot ◽  
Total Cell Population

ABSTRACT We have studied the effect of LHRH and neuropeptide Y (NPY) on prolactin (PRL) mRNA levels in pituitary reaggregate cell cultures from 14-day-old female rats, by means of in situ hybridization and Northern blot analysis. As estimated by computer-image analysis, addition of LHRH on day 5 in culture for 40 h resulted in a 37% increase in the total cytoplasmic areas of cells containing PRL mRNA, visualized using a digoxigenin-labelled PRL cRNA. The size of individual PRL-expressing cells was not influenced, nor was the content of PRL mRNA per cell. A similar effect of LHRH was found by dot blot hybridization of extracted RNA. PRL mRNA levels were not affected by NPY. LHRH induced a 29% increase in the number of PRL mRNA-expressing cells processing through the S phase of the cell cycle, visualized by the incorporation of [3H]thymidine ([3H]T) into DNA over 16 h. The fraction of [3H]T-labelled cells was 10–12% of the total cell population. NPY did not influence the number of [3H]T-positive cells expressing PRL mRNA, but completely blocked the effect of LHRH on the latter population. The present data suggest that LHRH, probably via a paracrine action of gonadotrophs, stimulates the recruitment of new lactotrophs, an action which is negatively modulated by NPY. Since the magnitude of this effect was the same in the total pituitary cell population as in cells processing through the S phase of the cell cycle and presumably mitosis, recruitment of lactotrophs seems to be based on differentiation of progenitor or immature cells into PRL-expressing cells, rather than on a mitogenic action on pre-existing lactotrophs alone.

Mitosis-specific phosphorylation of nucleolin by p34cdc2 protein kinase

1990 ◽  
Vol 10 (7) ◽  
pp. 3607-3618
Author(s):  
P Belenguer ◽  
M Caizergues-Ferrer ◽  
J C Labbé ◽  
M Dorée ◽  
F Amalric
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Control ◽  
Nucleolar Organizer ◽  
Serine Phosphorylation ◽  
Nucleolar Organizer Regions ◽  
Rdna Transcription ◽  
Amino Terminal ◽  
Nucleolar Chromatin

Nucleolin is a ubiquitous multifunctional protein involved in preribosome assembly and associated with both nucleolar chromatin in interphase and nucleolar organizer regions on metaphasic chromosomes in mitosis. Extensive nucleolin phosphorylation by a casein kinase (CKII) occurs on serine in growing cells. Here we report that while CKII phosphorylation is achieved in interphase, threonine phosphorylation occurs during mitosis. We provide evidence that this type of in vivo phosphorylation involves a mammalian homolog of the cell cycle control Cdc2 kinase. In vitro M-phase H1 kinase from starfish oocytes phosphorylated threonines in a TPXK motif present nine times in the amino-terminal part of the protein. The same sites which matched the p34cdc2 consensus phosphorylation sequence were used in vivo during mitosis. We propose that successive Cdc2 and CKII phosphorylation could modulate nucleolin function in controlling cell cycle-dependent nucleolar function and organization. Our results, along with previous studies, suggest that while serine phosphorylation is related to nucleolin function in the control of rDNA transcription, threonine phosphorylation is linked to mitotic reorganization of nucleolar chromatin.

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