Evidence for a role of calmodulin in serum stimulation of Na+ influx in human fibroblasts.

Intracellular free calcium ([Ca2+]i) has been proposed to play an important part in the regulation of the cell cycle. Although a number of studies have shown that stimulation of quiescent cells with growth factors causes an immediate rise in [Ca2+]i (Rabinovitch et al., 1986; Vincentini and Villereal, 1986; Hesketh et al., 1988; Tucker et al., 1989, Wahl et al., 1990), a causal relationship between the [Ca2+]i transient and the ability of the cells to reenter the cell cycle has not been firmly established. We have found that blocking the mitogen-induced elevation of [Ca2+]i with the cytoplasmic [Ca2+]i buffer dimethyl BAPTA (dmBAPTA) also blocks subsequent entry of cells into S phase. The dose response curves for inhibition of serum stimulation of [Ca2+]i and DNA synthesis by dmBAPTA are virtually identical including an anomalous stimulation observed at low levels of dmBAPTA. Reversal of the [Ca2+]i buffering effect of dmBAPTA by transient exposure of the cells to the Ca2+ ionophore ionomycin also reverses the inhibition of DNA synthesis 20-24 h later. Ionomycin by itself does not stimulate DNA synthesis. These data are consistent with the conclusion that a transient increase in [Ca2+]i occurring shortly after serum stimulation of quiescent fibroblasts is necessary but not sufficient for subsequent entry of the cells into S phase. This study is the first to show a direct relationship between early serum stimulated Cai2+ increase and subsequent DNA synthesis in human cells. It also goes beyond recent studies on BALB/3T3 cells by providing dose response data and demonstrating reversibility, which are strong indications of a cause and effect relationship.

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Existence of different Fos/Jun complexes during the G0-to-G1 transition and during exponential growth in mouse fibroblasts: differential role of Fos proteins

Molecular and Cellular Biology ◽

10.1128/mcb.12.11.5015-5023.1992 ◽

1992 ◽

Vol 12 (11) ◽

pp. 5015-5023

Author(s):

K Kovary ◽

R Bravo

Keyword(s):

Exponential Growth ◽

S Phase ◽

3T3 Cells ◽

Mouse Fibroblasts ◽

Quiescent Cells ◽

Serum Stimulation ◽

Fos Protein ◽

Swiss 3T3 ◽

Stimulation Of

We have determined the different Fos/Jun complexes present in Swiss 3T3 cells either following serum stimulation of quiescent cells or during exponential growth by immunoprecipitation analyses. We have shown that while c-Fos is the major Fos protein associated with the Jun proteins (c-Jun, JunB, and JunD) soon after serum stimulation, at later times Fra-1 and Fra-2 are the predominant Fos proteins associated with the different Jun proteins. During exponential growth, the synthesis of Fra-1 and Fra-2 is maintained at a significant level, in contrast to c-Fos and FosB, which are expressed at very low or undetectable levels. Consequently, Fra-1 and Fra-2 are the main Fos proteins complexed with the Jun proteins in asynchronously growing cells. To determine whether the Fos proteins are differentially required during the G0-to-G1 transition and exponential growth for the entrance into S phase, we microinjected affinity-purified antibodies directed against c-Fos, FosB, Fra-1, and Fra-2. We have found that while the activities of c-Fos and FosB are required mostly during the G0-to-G1 transition, Fra-1 and Fra-2 are involved both in the G0-to-G1 transition and in asynchronous growth.

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The role of ultrasound-induced cavitation in the ‘in vitro’ stimulation of collagen synthesis in human fibroblasts

Ultrasonics ◽

10.1016/0041-624x(80)90050-5 ◽

1980 ◽

Vol 18 (1) ◽

pp. 33-37 ◽

Cited By ~ 61

Author(s):

D.F. Webster ◽

W. Harvey ◽

M. Dyson ◽

J.B. Pond

Keyword(s):

Collagen Synthesis ◽

Human Fibroblasts ◽

Stimulation Of

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The chromatin remodeller CHD8 is required for E2F-dependent transcription activation of S-phase genes

Nucleic Acids Research ◽

10.1093/nar/gkt1161 ◽

2013 ◽

Vol 42 (4) ◽

pp. 2185-2196 ◽

Cited By ~ 40

Author(s):

Alicia Subtil-Rodríguez ◽

Elena Vázquez-Chávez ◽

María Ceballos-Chávez ◽

Manuel Rodríguez-Paredes ◽

José I. Martín-Subero ◽

...

Keyword(s):

Target Genes ◽

Transcription Activation ◽

S Phase ◽

Specific Expression ◽

Quiescent Cells ◽

Serum Stimulation ◽

Chromatin Configuration ◽

On Chip ◽

Stimulation Of

Abstract The precise regulation of S-phase–specific genes is critical for cell proliferation. How the repressive chromatin configuration mediated by the retinoblastoma protein and repressor E2F factors changes at the G1/S transition to allow transcription activation is unclear. Here we show ChIP-on-chip studies that reveal that the chromatin remodeller CHD8 binds ∼2000 transcriptionally active promoters. The spectrum of CHD8 target genes was enriched in E2F-dependent genes. We found that CHD8 binds E2F-dependent promoters at the G1/S transition but not in quiescent cells. Consistently, CHD8 was required for G1/S-specific expression of these genes and for cell cycle re-entry on serum stimulation of quiescent cells. We also show that CHD8 interacts with E2F1 and, importantly, loading of E2F1 and E2F3, but not E2F4, onto S-specific promoters, requires CHD8. However, CHD8 recruiting is independent of these factors. Recruiting of MLL histone methyltransferase complexes to S-specific promoters was also severely impaired in the absence of CHD8. Furthermore, depletion of CHD8 abolished E2F1 overexpression-dependent S-phase stimulation of serum-starved cells, highlighting the essential role of CHD8 in E2F-dependent transcription activation.

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Serum stimulation of sodium transport in human fibroblasts containing low and high levels of intracellular sodium

The Journal of Membrane Biology ◽

10.1007/bf01870705 ◽

1986 ◽

Vol 92 (2) ◽

pp. 163-170 ◽

Cited By ~ 2

Author(s):

Gillian Spurlock ◽

Kevin Morgan ◽

M. Afzal Mir

Keyword(s):

Sodium Transport ◽

Human Fibroblasts ◽

Intracellular Sodium ◽

Serum Stimulation ◽

Stimulation Of

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Existence of different Fos/Jun complexes during the G0-to-G1 transition and during exponential growth in mouse fibroblasts: differential role of Fos proteins.

Molecular and Cellular Biology ◽

10.1128/mcb.12.11.5015 ◽

1992 ◽

Vol 12 (11) ◽

pp. 5015-5023 ◽

Cited By ~ 127

Author(s):

K Kovary ◽

R Bravo

Keyword(s):

Exponential Growth ◽

S Phase ◽

3T3 Cells ◽

Mouse Fibroblasts ◽

Quiescent Cells ◽

Serum Stimulation ◽

Fos Protein ◽

Swiss 3T3 ◽

Stimulation Of

We have determined the different Fos/Jun complexes present in Swiss 3T3 cells either following serum stimulation of quiescent cells or during exponential growth by immunoprecipitation analyses. We have shown that while c-Fos is the major Fos protein associated with the Jun proteins (c-Jun, JunB, and JunD) soon after serum stimulation, at later times Fra-1 and Fra-2 are the predominant Fos proteins associated with the different Jun proteins. During exponential growth, the synthesis of Fra-1 and Fra-2 is maintained at a significant level, in contrast to c-Fos and FosB, which are expressed at very low or undetectable levels. Consequently, Fra-1 and Fra-2 are the main Fos proteins complexed with the Jun proteins in asynchronously growing cells. To determine whether the Fos proteins are differentially required during the G0-to-G1 transition and exponential growth for the entrance into S phase, we microinjected affinity-purified antibodies directed against c-Fos, FosB, Fra-1, and Fra-2. We have found that while the activities of c-Fos and FosB are required mostly during the G0-to-G1 transition, Fra-1 and Fra-2 are involved both in the G0-to-G1 transition and in asynchronous growth.

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