scholarly journals THE SYNTHESIS OF ACIDIC CHROMOSOMAL PROTEINS DURING THE CELL CYCLE OF HELA S-3 CELLS

1972 ◽  
Vol 52 (2) ◽  
pp. 308-315 ◽  
Author(s):  
T. W. Borun ◽  
G. S. Stein
Keyword(s):  
Cell Cycle ◽  
Protein Synthesis ◽  
Protein Fraction ◽  
Polyacrylamide Gel ◽  
Nuclear Fraction ◽  
Chromosomal Protein ◽  
Chromosomal Proteins ◽  
Kinetics Of ◽  
Mitotic Cells

The kinetics of acidic residual chromosomal protein synthesis and transport were studied throughout the cell cycle in HeLa S-3 cells synchronized by 2 mM thymidine block and selective detachment of mitotic cells. Pulse labeling the cells with leucine-3H for 2 min and then "chasing" the radioactive proteins for up to 3 hr showed that the amount of protein synthesized, transported, and retained in the acidic residual chromosomal protein fraction is greater immediately after mitosis and later in G1 than in the S or G2 phases of the cell cycle. During S, only 20–25% of the proteins synthesized and transported to the acidic residual chromosomal protein fraction are chased during the first 2 hr after pulse labeling, whereas up to 40% of the material entering the residual nuclear fraction in mitosis, G1, and G2 leaves during a 2 hr chase. Polyacrylamide gel electrophoretic profiles of these proteins, at various times after pulse labeling, reveal that the turnover of individual polypeptides within this fraction has kinetics of synthesis and turnover which are markedly different from one another and undergo stage-specific changes.

scholarly journals Non-histone chromosomal proteins. Evidence for their role in mediating the binding of histones to deoxyribonucleic acid during the cell cycle

1974 ◽  
Vol 139 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Gary S. Stein ◽  
Gale Hunter ◽  
Lena Lavie
Keyword(s):  
Cell Cycle ◽  
Deoxyribonucleic Acid ◽  
Sodium Deoxycholate ◽  
S Phase ◽  
Template Activity ◽  
Chromosomal Proteins ◽  
Ionic Detergent ◽  
Selective Dissociation ◽  
Chromatin Template ◽  
Mitotic Cells

By selective dissociation of histones with the ionic detergent sodium deoxycholate, we have demonstrated that these basic chromosomal polypeptides, which are effective inhibitors of transcription, are more tenaciously bound to DNA in mitotic than in S-phase chromatin. Evidence is presented which suggests that cell-cycle-stage-specific non-histone chromosomal proteins can account for such variations in the association of histones with DNA. When chromatin is reconstituted with DNA and histones are pooled from S-phase and mitotic cells and either S-phase or mitotic non-histone chromosomal proteins, a preferential extraction of histones with sodium deoxycholate from chromatin reconstituted with S-phase rather than mitotic non-histone chromosomal proteins is observed. In contrast, the extractability of histones with sodium deoxycholate from nucleohistone complexes reconstituted with DNA pooled from S-phase and mitotic cells and either S-phase or mitotic histones is identical. Since non-histone chromosomal proteins rather than histones are responsible for the differences in chromatin template activity during S-phase and mitosis, we propose that non-histone chromosomal proteins may modify gene expression during the cell cycle by mediating the binding of histones to DNA.

scholarly journals THE SYNTHESES OF DEOXYRIBONUCLEIC ACID AND HISTONE IN THE ONION ROOT MERISTEM

1967 ◽  
Vol 33 (3) ◽  
pp. 451-467 ◽  
Author(s):  
David P. Bloch ◽  
Robert A. MacQuigg ◽  
Sheilah D. Brack ◽  
Jung-Rung Wu
Keyword(s):  
Protein Synthesis ◽  
Dna Synthesis ◽  
Deoxyribonucleic Acid ◽  
Root Meristem ◽  
The Other ◽  
Chromosomal Protein ◽  
Chromosomal Proteins ◽  
Onion Root ◽  
Histone Synthesis ◽  
The Times

A comparison of the times necessary to incorporate tritium-labeled lysine and arginine into histones and tritium-labeled thymidine into DNA indicates that the periods of DNA and histone synthesis prior to division closely coincide. (The comparison was made by determining the times necessary, after pulse labeling, for cells with marked chromosomes to enter and then leave the division stages.) An additional period of chromosomal protein synthesis, of short duration, occurs late in interphase. Most of the chromosomal proteins appear either to be synthesized in the nucleus or to migrate there shortly after synthesis. Much of this protein is conserved from one division to the next. Studies of the effects of puromycin and fluorodeoxyuridine on the syntheses of DNA and histone suggest that continuation of DNA synthesis is dependent on a concurrent protein synthesis. Histone synthesis, on the other hand, can proceed at a normal rate under conditions in which DNA synthesis is inhibited.

Platelet Microtubule Subunit Proteins

1979 ◽  
Vol 42 (05) ◽  
pp. 1630-1633 ◽  
Author(s):  
A G Castle ◽  
N Crawford
Keyword(s):  
Epithelial Cells ◽  
Gel Electrophoresis ◽  
Blood Platelets ◽  
Polyacrylamide Gel Electrophoresis ◽  
Polyacrylamide Gel ◽  
Lens Epithelial Cells ◽  
Molecular Weights ◽  
Kinetics Of ◽  
Microtubular Structures

SummaryBlood platelets contain microtubule proteins (tubulin and HMWs) which can be polymerised “in vitro” to form structures which resemble the microtubules seen in the intact platelet. Platelet tubulin is composed of two non-identical subunits a and p tubulin which have molecular weights around 55,000 but can be resolved in alkaline SDS-polyacrylamide gel electrophoresis. These subunits associate as dimers with sedimentation coefficients of about 5.7 S although it is not known whether the dimer protein is a homo- or hetero-dimer. The dimer tubulin binds the anti-mitotic drug colchicine and the kinetics of this binding are similar to those reported for neurotubulins. Platelet microtubules also contain two HMW proteins which appear to be essential and integral components of the fully assembled microtubule. These proteins have molecular weights greater than 200,000 daltons. Fluorescent labelled antibodies to platelet and brain tubulins stain long filamentous microtubular structures in bovine lens epithelial cells and this pattern of staining is prevented by exposing the cells to conditions known to cause depolymerisation of cell microtubules.

Kinetics of Protein Synthesis in Enucleate Frog Oocytes

Science ◽  
1968 ◽  
Vol 160 (3832) ◽  
pp. 1115-1117 ◽  
Author(s):  
R. E. Ecker ◽  
L. D. Smith ◽  
S. Subtelny
Keyword(s):  
Protein Synthesis ◽  
Kinetics Of ◽  
Kinetics Of Protein Synthesis

scholarly journals A protein synthesis-dependent increase in E2F1 mRNA correlates with growth regulation of the dihydrofolate reductase promoter.

1993 ◽  
Vol 13 (3) ◽  
pp. 1610-1618 ◽  
Author(s):  
J E Slansky ◽  
Y Li ◽  
W G Kaelin ◽  
P J Farnham
Keyword(s):  
Cell Cycle ◽  
Protein Synthesis ◽  
Phase Boundary ◽  
Dihydrofolate Reductase ◽  
Transcription Initiation ◽  
Growth Regulation ◽  
Cellular Proliferation ◽  
Protein S ◽  
S Phase ◽  
Dependent Manner

Enhanced expression of genes involved in nucleotide biosynthesis, such as dihydrofolate reductase (DHFR), is a hallmark of entrance into the DNA synthesis (S) phase of the mammalian cell cycle. To investigate the regulated expression of the DHFR gene, we stimulated serum-starved NIH 3T3 cells to synchronously reenter the cell cycle. Our previous results show that a cis-acting element at the site of DHFR transcription initiation is necessary for serum regulation. Recently, this element has been demonstrated to bind the cloned transcription factor E2F. In this study, we focused on the role of E2F in the growth regulation of DHFR. We demonstrated that a single E2F site, in the absence or presence of other promoter elements, was sufficient for growth-regulated promoter activity. Next, we showed that the increase in DHFR mRNA at the G1/S-phase boundary required protein synthesis, raising the possibility that a protein(s) lacking in serum-starved cells is required for DHFR transcription. We found that, similar to DHFR mRNA expression, levels of murine E2F1 mRNA were low in serum-starved cells and increased at the G1/S-phase boundary in a protein synthesis-dependent manner. Furthermore, in a cotransfection experiment, expression of human E2F1 stimulated the DHFR promoter 22-fold in serum-starved cells. We suggest that E2F1 may be the key protein required for DHFR transcription that is absent in serum-starved cells. Expression of E2F also abolished the serum-stimulated regulation of the DHFR promoter and resulted in transcription patterns similar to those seen with expression of the adenoviral oncoprotein E1A. In summary, we provide evidence for the importance of E2F in the growth regulation of DHFR and suggest that alterations in the levels of E2F may have severe consequences in the control of cellular proliferation.

scholarly journals Identification in skeletal muscle of a distinct extracellular pool of amino acids, and its role in protein synthesis

1971 ◽  
Vol 121 (5) ◽  
pp. 817-827 ◽  
Author(s):  
R. C. Hider ◽  
E. B. Fern ◽  
D. R. London
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Incubation Medium ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Longus Muscle ◽  
Kinetics Of

1. The kinetics of radioactive labelling of extra- and intra-cellular amino acid pools and protein of the extensor digitorum longus muscle were studied after incubations with radioactive amino acids in vitro. 2. The results indicated that an extracellular pool could be defined, the contents of which were different from those of the incubation medium. 3. It was concluded that amino acids from the extracellular pool, as defined in this study, were incorporated directly into protein.

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