Cell Cycle Dependent Agglutinability, Distribution of Concanavalin a Binding Sites and Surface Morphology of Normal and Transformed Fibroblasts

1975 ◽  
pp. 221-244 ◽  
Author(s):  
J. G. Collard ◽  
J. H. M. Temmink ◽  
L. A. Smets
Keyword(s):  
Cell Cycle ◽  
Surface Morphology ◽  
Concanavalin A ◽  
Binding Sites ◽  
Transformed Fibroblasts ◽  
Cycle Dependent

Differences in density of Concanavalin A-binding sites due to differences in surface morphology of suspended normal and transformed 3T3 fibroblasts

1975 ◽  
Vol 19 (1) ◽  
pp. 21-32
Author(s):  
J.G. Collard ◽  
J.H. Temmink
Keyword(s):  
Surface Morphology ◽  
Concanavalin A ◽  
Binding Sites ◽  
3T3 Cells ◽  
Con A ◽  
3T3 Fibroblasts ◽  
Transformed Fibroblasts ◽  
Transmission Electron ◽  
The Difference ◽  
Electron Microscopes

Calculations of the density of Concanavalin A (Con A)-binding sites on normal and transformed fibroblasts have, as yet, been based on the unproven assumption that suspended cells are smooth spheres. We studied the surface morphology of suspended normal and transformed fibroblasts with scanning and transmission electron microscopes, and found a large difference in surface morphology between suspended normal and transformed 3T3 cells. When this difference in surface morphology was taken into account, the estimated cell surface area of normal 3T3 cells was approximately seven times larger than that of transformed 3T3 cells. Since equal numbers of 3H-Con A molecules are bound on normal and transformed cells, the density of Con A-binding sites is approximately seven times greater on transformed than on normal 3T3 cells. The difference in density of Con A-binding sites between normal and transformed fibroblasts might be sufficient to explain the difference in agglutination response, as originally suggested by Burger, and may also be the cause of the different degrees of clustering of Con A-binding sites on the plasma membrane of these cells.

scholarly journals Subunit composition determines E2F DNA-binding site specificity.

1997 ◽  
Vol 17 (12) ◽  
pp. 6994-7007 ◽  
Author(s):  
Y Tao ◽  
R F Kassatly ◽  
W D Cress ◽  
J M Horowitz
Keyword(s):  
Cell Cycle ◽  
Dna Binding ◽  
Binding Sites ◽  
Dna Bending ◽  
Susceptibility Gene ◽  
Specific Sequence ◽  
Cellular Genes ◽  
Cycle Dependent

The product of the retinoblastoma (Rb) susceptibility gene, Rb-1, regulates the activity of a wide variety of transcription factors, such as E2F, in a cell cycle-dependent fashion. E2F is a heterodimeric transcription factor composed of two subunits each encoded by one of two related gene families, denoted E2F and DP. Five E2F genes, E2F-1 through E2F-5, and two DP genes, DP-1 and DP-2, have been isolated from mammals, and heterodimeric complexes of these proteins are expressed in most, if not all, vertebrate cells. It is not yet clear whether E2F/DP complexes regulate overlapping and/or specific cellular genes. Moreover, little is known about whether Rb regulates all or a subset of E2F-dependent genes. Using recombinant E2F, DP, and Rb proteins prepared in baculovirus-infected cells and a repetitive immunoprecipitation-PCR procedure (CASTing), we have identified consensus DNA-binding sites for E2F-1/DP-1, E2F-1/DP-2, E2F-4/DP-1, and E2F-4/DP-2 complexes as well as an Rb/E2F-1/DP-1 trimeric complex. Our data indicate that (i) E2F, DP, and Rb proteins each influence the selection of E2F-binding sites; (ii) E2F sites differ with respect to their intrinsic DNA-bending properties; (iii) E2F/DP complexes induce distinct degrees of DNA bending; and (iv) complex-specific E2F sites selected in vitro function distinctly as regulators of cell cycle-dependent transcription in vivo. These data indicate that the specific sequence of an E2F site may determine its role in transcriptional regulation and suggest that Rb/E2F complexes may regulate subsets of E2F-dependent cellular genes.

scholarly journals Surface morphology and agglutinability with concanavalin A in normal and transformed murine fibroblasts.

1976 ◽  
Vol 68 (1) ◽  
pp. 101-112 ◽  
Author(s):  
J G Collard ◽  
J H Temmink
Keyword(s):  
Surface Morphology ◽  
Concanavalin A ◽  
Ethylenediaminetetraacetic Acid ◽  
Simian Virus 40 ◽  
Cell Surfaces ◽  
3T3 Cells ◽  
Con A ◽  
Transformed Fibroblasts ◽  
Murine Fibroblasts

The surface morphology of attached and suspended normal and transformed fibroblasts has been studied with the scanning electron microscope. Normal murine fibroblasts (3T3) grow in vitro with widely extended leading lamellae. During most parts of the cell cycle the surfaces of these cells are practically free of microvilli. When the cells round up for mitosis, their cell surfaces become adorned with many microvilli. In contrast, simian virus 40-transformed fibroblasts (SV3T3) grow more compact, and their cell surfaces remain smooth throughout the life cycle. When confluent 3T3 and SV3T3 cells are suspended with ethylenediaminetetraacetic acid (EDTA) for agglutination assays, similar differences in surface morphology are found: 3T3 cells always bear many microvilli, whereas most SV3T3 cells are essentially free of microvilli. The addition of concanavalin A (Con A) does not influence the surface morphology of the suspended cells. The morphological differences described here may be important for the agglutination process of the normal and transformed 3T3 cells, because they affect the real cell surface area and thus the density of Con A-binding sites.

Transcription of the E2F-1 gene is rendered cell cycle dependent by E2F DNA-binding sites within its promoter

1994 ◽  
Vol 14 (10) ◽  
pp. 6607-6615
Author(s):  
E Neuman ◽  
E K Flemington ◽  
W R Sellers ◽  
W G Kaelin
Keyword(s):  
Cell Cycle ◽  
Binding Sites ◽  
Mammalian Cells ◽  
Mrna Abundance ◽  
Dna Binding Sites ◽  
Cell Cycle Dependence ◽  
Transcription Factor E2f ◽  
Cycle Dependent

The cell cycle-regulatory transcription factor E2F-1 is regulated by interactions with proteins such as the retinoblastoma gene product and by cell cycle-dependent alterations in E2F-1 mRNA abundance. To better understand this latter phenomenon, we have isolated the human E2F-1 promoter. The human E2F-1 promoter, fused to a luciferase cDNA, gave rise to cell cycle-dependent luciferase activity upon transfection into mammalian cells in a manner which paralleled previously reported changes in E2F-1 mRNA abundance. The E2F-1 promoter contains four potential E2F-binding sites organized as two imperfect palindromes. Gel shift and transactivation studies suggested that these sites can bind to E2F in vitro and in vivo. Mutation of the two E2F palindromes abolished the cell cycle dependence of the E2F-1 promoter. Thus, E2F-1 appears to be regulated at the level of transcription, and this regulation is due, at least in part, to binding of one or more E2F family members to the E2F-1 promoter.

scholarly journals CELL CYCLE-DEPENDENT CHANGES IN THE SURFACE MEMBRANE AS DETECTED WITH [3H]CONCANAVALIN A

1973 ◽  
Vol 58 (2) ◽  
pp. 491-497 ◽  
Author(s):  
Kenneth D. Noonan ◽  
Arnold J. Levine ◽  
Max M. Burger
Keyword(s):  
Cell Cycle ◽  
Concanavalin A ◽  
Surface Membrane ◽  
Cycle Dependent

scholarly journals Transcription of the E2F-1 gene is rendered cell cycle dependent by E2F DNA-binding sites within its promoter.

1994 ◽  
Vol 14 (10) ◽  
pp. 6607-6615 ◽  
Author(s):  
E Neuman ◽  
E K Flemington ◽  
W R Sellers ◽  
W G Kaelin
Keyword(s):  
Cell Cycle ◽  
Binding Sites ◽  
Mammalian Cells ◽  
Mrna Abundance ◽  
Dna Binding Sites ◽  
Cell Cycle Dependence ◽  
Transcription Factor E2f ◽  
Cycle Dependent

The cell cycle-regulatory transcription factor E2F-1 is regulated by interactions with proteins such as the retinoblastoma gene product and by cell cycle-dependent alterations in E2F-1 mRNA abundance. To better understand this latter phenomenon, we have isolated the human E2F-1 promoter. The human E2F-1 promoter, fused to a luciferase cDNA, gave rise to cell cycle-dependent luciferase activity upon transfection into mammalian cells in a manner which paralleled previously reported changes in E2F-1 mRNA abundance. The E2F-1 promoter contains four potential E2F-binding sites organized as two imperfect palindromes. Gel shift and transactivation studies suggested that these sites can bind to E2F in vitro and in vivo. Mutation of the two E2F palindromes abolished the cell cycle dependence of the E2F-1 promoter. Thus, E2F-1 appears to be regulated at the level of transcription, and this regulation is due, at least in part, to binding of one or more E2F family members to the E2F-1 promoter.

scholarly journals Cell cycle-dependent nucleosome occupancy at cohesin binding sites in yeast chromosomes

Genomics ◽  
2008 ◽  
Vol 91 (3) ◽  
pp. 274-280 ◽  
Author(s):  
Jie Liu ◽  
Daniel M. Czajkowsky ◽  
Shoudan Liang ◽  
Zhifeng Shao
Keyword(s):  
Cell Cycle ◽  
Binding Sites ◽  
Nucleosome Occupancy ◽  
Cycle Dependent

scholarly journals Mitochondrial adenosine triphosphatase of the fission yeast Schizosaccharomyces pombe 972h-. Changes in inhibitor sensitivities during the cell cycle indicate similarities and differences in binding sites

1977 ◽  
Vol 162 (3) ◽  
pp. 581-590 ◽  
Author(s):  
D Lloyd ◽  
S W Edwards
Keyword(s):  
Cell Cycle ◽  
Schizosaccharomyces Pombe ◽  
Binding Sites ◽  
Adenosine Triphosphatase ◽  
Specific Activity ◽  
Inhibitor Binding ◽  
Titration Curves ◽  
Catalytic Sites ◽  
Cycle Dependent ◽  
Similar Site

1. We used 11 different inhibitors of energy conservation as inhibitors of ATPase (adenosine triphosphatase) in extracts of Schizosaccharomyces pombe obtained from cells at different stages of the cell cycle. 2. All the inhibitors showed cell-cycle-dependent variations in their I50 values (microng of inhibitor/mg of protein giving 50% inhibition of inhibitor-sensitive ATPase at pH 8.6). 3. From the sensitivity profiles through the cell cycle it was concluded that: (a) oligomycin, venturicidin, triethyltin sulphate and dibutylchloromethyltin chloride all act at closely associated site(s); (b) NN'-dicyclohexylcarbodi-imide and leucinostatin both act at a similar site, which is, however, distinct from that at which other inhibitors of the membrane factor (Fo) act. 4. The variations in I50 values for efrapeptin closely followed changes in specific activity of ATPase, as would be expected for an inhibitor acting at catalytic sites; these fluctuations were different from those for aurovertin, Dio-9, 4-chloro-7-nitrobenzofurazan, quercetin and spegazzinine, all of which show different sensitivity profiles from one another. 5. Anomalous stepwise inhibitor-titration curves were obtained for spegazzinine, NN'-dicyclohexylcarbodiimide, dibutylchloromethyltin chloride and leucinostatin. 6. Possible explanations are proposed for the discontinuous expression of inhibitor-binding sites during the cell cycle.

scholarly journals Transcription of the E2F-1 gene is rendered cell cycle dependent by E2F DNA-binding sites within its promoter.

1995 ◽  
Vol 15 (8) ◽  
pp. 4660-4660 ◽  
Author(s):  
E Neuman ◽  
E K Flemington ◽  
W R Sellers ◽  
W G Kaelin
Keyword(s):  
Cell Cycle ◽  
Dna Binding ◽  
Binding Sites ◽  
Dna Binding Sites ◽  
Cycle Dependent

scholarly journals Cell Cycle Control of Kaposi's Sarcoma-Associated Herpesvirus Latency Transcription by CTCF-Cohesin Interactions

2009 ◽  
Vol 83 (12) ◽  
pp. 6199-6210 ◽  
Author(s):  
Hyojeung Kang ◽  
Paul M. Lieberman
Keyword(s):  
Cell Cycle ◽  
Host Cell ◽  
Control Region ◽  
Binding Sites ◽  
Cell Cycle Control ◽  
Ctcf Binding ◽  
Dependent Manner ◽  
Cohesin Complex ◽  
A Cell ◽  
Cycle Dependent

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) latency is characterized by the highly regulated transcription of a few viral genes essential for genome maintenance and host cell survival. A major latency control region has been identified upstream of the divergent promoters for the multicistronic transcripts encoding LANA (ORF73), vCyclin (ORF72), and vFLIP (ORF71) and for the complementary strand transcript encoding K14 and vGPCR (ORF74). Previous studies have shown that this major latency control region is occupied by the cellular chromatin boundary factor CTCF and chromosome structural maintenance proteins SMC1, SMC3, and RAD21, which comprise the cohesin complex. Deletion of the CTCF-cohesin binding site caused an inhibition of cell growth and viral genome instability. We now show that the KSHV genes regulated by CTCF-cohesin are under cell cycle control and that mutation of the CTCF binding sites abolished cell cycle-regulated transcription. Cohesin subunits assembled at the CTCF binding sites and bound CTCF proteins in a cell cycle-dependent manner. Subcellular distribution of CTCF and colocalization with cohesins also varied across the cell cycle. Ectopic expression of Rad21 repressed CTCF-regulated transcription of KSHV lytic genes, and a Rad21-CTCF chimeric protein converted CTCF into an efficient transcriptional repressor of KSHV genes normally activated in the G2 phase. We conclude that cohesins interact with CTCF in mid-S phase and repress CTCF-regulated genes in a cell cycle-dependent manner. We propose that the CTCF-cohesin complex plays a critical role in regulating the cell cycle control of viral gene expression during latency and that failure to maintain cell cycle control of latent transcripts inhibits host cell proliferation and survival.

Sign in / Sign up

Export Citation Format

Share Document