Phosphorylation of serum response factor by casein kinase II: evidence against a role in growth factor regulation of fos expression

J R Manak; R Prywes

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Phosphorylation of serum response factor by casein kinase II: evidence against a role in growth factor regulation of fos expression

Journal article

Peer reviewed

Phosphorylation of serum response factor by casein kinase II: evidence against a role in growth factor regulation of fos expression

J R Manak and R Prywes

Oncogene, Vol.8(3), pp.703-711

03/1993

PMID: 8437853

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Abstract

Serum response factor (SRF) is a transcription factor involved in the serum and growth factor regulation of the c-fos gene. SRF is phosphorylated by casein kinase II (CKII), which causes a large increase in its DNA-binding activity. CKII activity has been shown to be stimulated by growth factors and serum. Since c-fos transcription is induced by a number of the same agents that stimulate CKII activity, and since fos activation and CKII stimulation demonstrate similar rapid kinetics, a role was proposed for CKII in regulating fos expression via its phosphorylation of SRF. In this report, we provide evidence against this hypothesis by using several different strategies. First, by immunoprecipitation of SRF from cells, we show that the phosphorylation state of SRF does not change upon growth factor treatment. Second, by two-dimensional electrophoresis of lysates from a cell line that overexpresses SRF, we show that, although SRF exists in the cell in several different isoforms, there is no change in their relative amounts upon serum stimulation. Third, we tested the activity of an SRF mutant that binds DNA at constitutively high levels irrespective of CKII phosphorylation. If phosphorylation is regulatory, this mutant would be expected to constitutively activate (or repress) fos expression. However, when overexpressed stably in cells this mutant had no effect on endogenous c-fos expression, suggesting that CKII phosphorylation of SRF is not the limiting event for fos activation.

Recombinant Fusion Proteins - biosynthesis

Amino Acid Sequence

Rabbits

Phosphorylation

Casein Kinase II

DNA-Binding Proteins - immunology

Chymotrypsin - metabolism

Gene Expression Regulation

Molecular Sequence Data

Electrophoresis, Gel, Two-Dimensional

Nuclear Proteins - metabolism

Nuclear Proteins - immunology

Trypsin - metabolism

Precipitin Tests

DNA-Binding Proteins - metabolism

Serum Response Factor

Transcription Factors - metabolism

Animals

Growth Substances - physiology

Genes, fos

Mice

Transcription Factors - immunology

3T3 Cells

Protein-Serine-Threonine Kinases - metabolism

Details

Title: Subtitle: Phosphorylation of serum response factor by casein kinase II: evidence against a role in growth factor regulation of fos expression
Creators: J R Manak - Department of Biological Sciences, Columbia University, New York, New York 10027
R Prywes
Resource Type: Journal article
Publication Details: Oncogene, Vol.8(3), pp.703-711
PMID: 8437853
NLM abbreviation: Oncogene
ISSN: 0950-9232
eISSN: 1476-5594
Publisher: England
Grant note: CA 50329-01 / NCI NIH HHS
Language: English
Date published: 03/1993
Academic Unit: Stead Family Department of Pediatrics; Biology; Craniofacial Anomalies Research Center
Record Identifier: 9983991956202771

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