Control of histone gene expression in Physarum polycephalum. I. Protein synthesis during the cell cycle

1982 ◽  
Vol 57 (1) ◽  
pp. 139-150
Author(s):  
P.N. Schofield ◽  
I.O. Walker
Keyword(s):  
Cell Cycle ◽  
Physarum Polycephalum ◽  
Specific Activity ◽  
S Phase ◽  
Histone Gene ◽  
Synchronous Cultures ◽  
Histone Gene Expression ◽  
Core Histones ◽  
G2 Phase ◽  
Histone Synthesis

Synchronous cultures of Physarum polycephalum were pulsed with [3H]lysine hydrochloride in S and G2 phases of the cell cycle. Plasmodial extracts were separated into nuclear, ribosomal and acid-soluble post-ribosomal cytoplasmic fractions. Core histones could be detected by staining in the nuclear fractions of both S and G2 phases, but were not detected by staining in the cytoplasmic fractions. Newly synthesized histone was present in S-phase nuclei but not in S-phase cytoplasm. The specific activity of newly synthesized histone in G2-phase nuclei decreased by at least 95% compared to S phase and no newly synthesized histone was observed in G2-phase cytoplasmic fractions. Thus histone synthesis is restricted to S phase. There are no free pools of histone in the cytoplasm of Physarum in either S or G2 phases of the cell cycle.

scholarly journals Distinct replication-independent and -dependent phases of histone gene expression during the Physarum cell cycle.

1987 ◽  
Vol 7 (5) ◽  
pp. 1933-1937 ◽  
Author(s):  
J J Carrino ◽  
V Kueng ◽  
R Braun ◽  
T G Laffler
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Dna Replication ◽  
Dna Synthesis ◽  
S Phase ◽  
Histone Gene ◽  
Histone Mrna ◽  
Histone Gene Expression ◽  
Tightly Coupled ◽  
G2 Phase

During the S phase of the cell cycle, histone gene expression and DNA replication are tightly coupled. In mitotically synchronous plasmodia of the myxomycete Physarum polycephalum, which has no G1 phase, histone mRNA synthesis begins in mid-G2 phase. Although histone gene transcription is activated in the absence of significant DNA synthesis, our data demonstrate that histone gene expression became tightly coupled to DNA replication once the S phase began. There was a transition from the replication-independent phase to the replication-dependent phase of histone gene expression. During the first phase, histone mRNA synthesis appears to be under direct cell cycle control; it was not coupled to DNA replication. This allowed a pool of histone mRNA to accumulate in late G2 phase, in anticipation of future demand. The second phase began at the end of mitosis, when the S phase began, and expression became homeostatically coupled to DNA replication. This homeostatic control required continuing protein synthesis, since cycloheximide uncoupled transcription from DNA synthesis. Nuclear run-on assays suggest that in P. polycephalum this coupling occurs at the level of transcription. While histone gene transcription appears to be directly switched on in mid-G2 phase and off at the end of the S phase by cell cycle regulators, only during the S phase was the level of transcription balanced with the rate of DNA synthesis.

Distinct replication-independent and -dependent phases of histone gene expression during the Physarum cell cycle

1987 ◽  
Vol 7 (5) ◽  
pp. 1933-1937
Author(s):  
J J Carrino ◽  
V Kueng ◽  
R Braun ◽  
T G Laffler
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Dna Replication ◽  
Dna Synthesis ◽  
S Phase ◽  
Histone Gene ◽  
Histone Mrna ◽  
Histone Gene Expression ◽  
Tightly Coupled ◽  
G2 Phase

During the S phase of the cell cycle, histone gene expression and DNA replication are tightly coupled. In mitotically synchronous plasmodia of the myxomycete Physarum polycephalum, which has no G1 phase, histone mRNA synthesis begins in mid-G2 phase. Although histone gene transcription is activated in the absence of significant DNA synthesis, our data demonstrate that histone gene expression became tightly coupled to DNA replication once the S phase began. There was a transition from the replication-independent phase to the replication-dependent phase of histone gene expression. During the first phase, histone mRNA synthesis appears to be under direct cell cycle control; it was not coupled to DNA replication. This allowed a pool of histone mRNA to accumulate in late G2 phase, in anticipation of future demand. The second phase began at the end of mitosis, when the S phase began, and expression became homeostatically coupled to DNA replication. This homeostatic control required continuing protein synthesis, since cycloheximide uncoupled transcription from DNA synthesis. Nuclear run-on assays suggest that in P. polycephalum this coupling occurs at the level of transcription. While histone gene transcription appears to be directly switched on in mid-G2 phase and off at the end of the S phase by cell cycle regulators, only during the S phase was the level of transcription balanced with the rate of DNA synthesis.

scholarly journals Maximal binding levels of an H1 histone gene-specific factor in S-phase correlate with maximal H1 gene transcription.

1988 ◽  
Vol 8 (10) ◽  
pp. 4576-4578 ◽  
Author(s):  
S Dalton ◽  
J R Wells
Keyword(s):  
Cell Cycle ◽  
Nucleic Acids ◽  
Gene Transcription ◽  
S Phase ◽  
Histone Gene ◽  
Specific Factor ◽  
Synchronized Cells ◽  
Phase Regulation ◽  
G2 Phase ◽  
Binding Component

Levels of trans-acting factor (H1-SF) binding to the histone H1 gene-specific motif (5'-AAACACA-3' [L. S. Coles and J. R. E. Wells, Nucleic Acids Res. 13:585-594, 1985]) increase 12-fold from G1 to S-phase in synchronized cells and decrease again in G2 phase of the cell cycle. Since the H1 element is required for S-phase expression of H1 genes (S. Dalton and J. R. E. Wells, EMBO J. 7:49-56, 1988), it is likely that the increased levels of H1-SF binding component play an important role in S-phase regulation of H1 gene transcription.

Maximal binding levels of an H1 histone gene-specific factor in S-phase correlate with maximal H1 gene transcription

1988 ◽  
Vol 8 (10) ◽  
pp. 4576-4578
Author(s):  
S Dalton ◽  
J R Wells
Keyword(s):  
Cell Cycle ◽  
Nucleic Acids ◽  
Gene Transcription ◽  
S Phase ◽  
Histone Gene ◽  
Specific Factor ◽  
Synchronized Cells ◽  
Phase Regulation ◽  
G2 Phase ◽  
Binding Component

Levels of trans-acting factor (H1-SF) binding to the histone H1 gene-specific motif (5'-AAACACA-3' [L. S. Coles and J. R. E. Wells, Nucleic Acids Res. 13:585-594, 1985]) increase 12-fold from G1 to S-phase in synchronized cells and decrease again in G2 phase of the cell cycle. Since the H1 element is required for S-phase expression of H1 genes (S. Dalton and J. R. E. Wells, EMBO J. 7:49-56, 1988), it is likely that the increased levels of H1-SF binding component play an important role in S-phase regulation of H1 gene transcription.

Some evidence for replication-transcription coupling in Physarum polycephalum

1975 ◽  
Vol 18 (1) ◽  
pp. 27-39
Author(s):  
H. Fouquet ◽  
R. Bohme ◽  
R. Wick ◽  
H.W. Sauer ◽  
K. Scheller
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Dna Sequences ◽  
Physarum Polycephalum ◽  
Rna Synthesis ◽  
Selective Inhibition ◽  
S Phase ◽  
Dna Molecules ◽  
Uridine Incorporation ◽  
G2 Phase

Hydroxyurea, at concentrations of 40–60 mM, selectively and effectively blocked incorporation of thymidine into DNA. Inhibition occurred within 5–10 min of application of the agent when DNA synthesis was in progress, while the onset of replication at the beginning of S-phase and DNA synthesis in G2 phase were not affected. Uridine incorporation into TCA-precipitable material, in the presence of hydroxyurea, was significantly (up to 70%) inhibited in early S-phase of the cell cycle. Selective inhibition of RNA synthesis was confirmed for RNA separated into rRNA-rich and poly(A)-rich RNA fractions and analysed by the 2 kinds of DNA-RNA hybridization reactions. Uridine incorporation into poly (A) RNA was also inhibited under conditions where cycloheximide prevented maturation of nascent DNA molecules in early S-phase. We assume that chromatin which is replicating early DNA sequences may be a more competent template for transcription.

scholarly journals The E2F transcription factor activates a replication-dependent human H2A gene in early S phase of the cell cycle.

1996 ◽  
Vol 16 (5) ◽  
pp. 1889-1895 ◽  
Author(s):  
F Oswald ◽  
T Dobner ◽  
M Lipp
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Transcription Factor ◽  
Transcriptional Activation ◽  
Promoter Region ◽  
S Phase ◽  
Histone Gene ◽  
Luciferase Reporter ◽  
Transcriptional Level ◽  
Histone Gene Expression

Histone gene expression is restricted to the S phase of the cell cycle. Control is mediated by a complex network of sequence-specific DNA-binding factors and protein-protein interactions in response to cell cycle progression. To further investigate the regulatory functions that are associated at the transcriptional level, we analyzed the regulation of a replication-dependent human H2A.1-H2B.2 gene pair. We found that transcription factor E2F binds specifically to an E2F recognition motif in the H2A.1 promoter region. Activation of the H2A.1 promoter by E2F-1 was shown by use of luciferase reporter constructs of the intergenic promoter region. Overexpression of the human retinoblastoma suppressor gene product RB suppressed E2F-1 mediated transcriptional activation, indicating an E2F-dependent regulation of promoter activity during the G1-to-S-phase transition. Furthermore, the activity of the H2A.1 promoter was also downregulated by overexpression of the RB-related p107, a protein that has been detected in S-phase-specific protein complexes of cyclin A, E2F, and cdk2. In synchronized HeLa cells, expression of luciferase activity was induced at the beginning of DNA synthesis and was dependent on the presence of an E2F-binding site in the H2A.1 promoter. Together with the finding that E2F-binding motifs are highly conserved in H2A promoters of other species, our results suggest that E2F plays an important role in the coordinate regulation of S-phase-specific histone gene expression.

Regulation of human histone gene expression during the HeLa cell cycle requires protein synthesis

1984 ◽  
Vol 4 (12) ◽  
pp. 2723-2734
Author(s):  
H L Sive ◽  
N Heintz ◽  
R G Roeder
Keyword(s):  
Cell Cycle ◽  
Protein Synthesis ◽  
S Phase ◽  
Histone Gene ◽  
Protein Synthesis Inhibitor ◽  
Protein Synthesis Inhibition ◽  
Synthesis Inhibitor ◽  
Synthesis Inhibition ◽  
Histone Mrnas ◽  
Histone Gene Expression

We have examined the effects of protein synthesis inhibition on histone gene expression during the HeLa cell cycle. Histone mRNAs, which normally are rapidly degraded in the absence of DNA synthesis, persist and increase in concentration when translation is inhibited before DNA replication is halted. This is not a function of polysomal shielding of these mRNAs from active degradation mechanisms since inhibitors of translation initiation alone effect stabilization and induction. The superinduction of histone mRNAs by protein synthesis inhibition is effective at the G1/S border, and in the S-phase and non-S-phase periods of the cell cycle. However, the relative increase in histone mRNA is greater when cells not synthesizing DNA are treated with a protein synthesis inhibitor than when S-phase cells are so treated. Non-histone mRNAs examined are not superinduced by translation inhibition. Transcription rates from both histone and non-histone genes increase after protein synthesis inhibition. Although the decrease in histone gene transcription associated with DNA synthesis inhibition is prevented and reversed by protein synthesis inhibition, we have no evidence that histone gene-specific transcriptional regulation is dependent on protein synthesis. Transcriptional increases may contribute to the superinduction effect but cannot explain its differential extent during the cell cycle, since these increases are similar when replicating or nonreplicating cells are treated with a protein synthesis inhibitor. We believe that changes in histone mRNA stability can account for much of the differential superinduction effect. Our results indicate a requirement for continuing protein synthesis in the cell cycle regulation of histone mRNAs.

scholarly journals Replication-dependent histone biosynthesis is coupled to cell-cycle commitment

2021 ◽  
Vol 118 (31) ◽  
pp. e2100178118
Author(s):  
Claire Armstrong ◽  
Sabrina L. Spencer
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Live Cell Imaging ◽  
Current Model ◽  
S Phase ◽  
Strong Increase ◽  
Key Factors ◽  
Histone Gene Expression ◽  
Small Pool ◽  
Histone Synthesis

The current model of replication-dependent (RD) histone biosynthesis posits that RD histone gene expression is coupled to DNA replication, occurring only in S phase of the cell cycle once DNA synthesis has begun. However, several key factors in the RD histone biosynthesis pathway are up-regulated by E2F or phosphorylated by CDK2, suggesting these processes may instead begin much earlier, at the point of cell-cycle commitment. In this study, we use both fixed- and live-cell imaging of human cells to address this question, revealing a hybrid model in which RD histone biosynthesis is first initiated in G1, followed by a strong increase in histone production in S phase of the cell cycle. This suggests a mechanism by which cells that have committed to the cell cycle build up an initial small pool of RD histones to be available for the start of DNA replication, before producing most of the necessary histones required in S phase. Thus, a clear distinction exists at completion of mitosis between cells that are born with the intention of proceeding through the cell cycle and replicating their DNA and cells that have chosen to exit the cell cycle and have no immediate need for histone synthesis.

scholarly journals Transcription of alpha-tubulin and histone H4 genes begins at the same point in the Physarum cell cycle.

1986 ◽  
Vol 102 (5) ◽  
pp. 1666-1670 ◽  
Author(s):  
J J Carrino ◽  
T G Laffler
Keyword(s):  
Cell Cycle ◽  
Gene Transcription ◽  
Blot Hybridization ◽  
S Phase ◽  
Histone Gene ◽  
Histone H4 ◽  
Alpha Tubulin ◽  
Periodic Cell ◽  
G2 Phase ◽  
Histone Gene Transcription

In naturally synchronous plasmodia of Physarum polycephalum, both tubulin and histone gene transcription define periodic cell cycle-regulated events. Using a slot-blot hybridization assay and Northern blot analysis, we have demonstrated that a major peak of accumulation of both alpha-tubulin and histone H4 transcripts occurs in late G2 phase. Nuclear transcription assays indicate that both genes are transcriptionally activated at the same point in the cell cycle: mid G2 phase. While the rate of tubulin gene transcription drops sharply at the M/S-phase boundary, the rate of histone gene transcription remains high through most of S phase. We conclude that the cell cycle regulation of tubulin expression occurs primarily at the level of transcription, while histone regulation involves both transcriptional and posttranscriptional controls. It is possible that the periodic expression of both histone and tubulin genes is triggered by a common cell cycle regulatory mechanism.

scholarly journals Regulation of human histone gene expression during the HeLa cell cycle requires protein synthesis.

1984 ◽  
Vol 4 (12) ◽  
pp. 2723-2734 ◽  
Author(s):  
H L Sive ◽  
N Heintz ◽  
R G Roeder
Keyword(s):  
Cell Cycle ◽  
Protein Synthesis ◽  
S Phase ◽  
Histone Gene ◽  
Protein Synthesis Inhibitor ◽  
Protein Synthesis Inhibition ◽  
Synthesis Inhibitor ◽  
Synthesis Inhibition ◽  
Histone Mrnas ◽  
Histone Gene Expression

We have examined the effects of protein synthesis inhibition on histone gene expression during the HeLa cell cycle. Histone mRNAs, which normally are rapidly degraded in the absence of DNA synthesis, persist and increase in concentration when translation is inhibited before DNA replication is halted. This is not a function of polysomal shielding of these mRNAs from active degradation mechanisms since inhibitors of translation initiation alone effect stabilization and induction. The superinduction of histone mRNAs by protein synthesis inhibition is effective at the G1/S border, and in the S-phase and non-S-phase periods of the cell cycle. However, the relative increase in histone mRNA is greater when cells not synthesizing DNA are treated with a protein synthesis inhibitor than when S-phase cells are so treated. Non-histone mRNAs examined are not superinduced by translation inhibition. Transcription rates from both histone and non-histone genes increase after protein synthesis inhibition. Although the decrease in histone gene transcription associated with DNA synthesis inhibition is prevented and reversed by protein synthesis inhibition, we have no evidence that histone gene-specific transcriptional regulation is dependent on protein synthesis. Transcriptional increases may contribute to the superinduction effect but cannot explain its differential extent during the cell cycle, since these increases are similar when replicating or nonreplicating cells are treated with a protein synthesis inhibitor. We believe that changes in histone mRNA stability can account for much of the differential superinduction effect. Our results indicate a requirement for continuing protein synthesis in the cell cycle regulation of histone mRNAs.

Sign in / Sign up

Export Citation Format

Share Document