Abstract
Histone H3 phosphorylation has been linked to various environmental stress responses and specific chromatin structure. The role of H3 phosphorylation in the osmotic stress response was investigated on the mouse mammary tumor virus (MMTV) promoter in different chromatin configurations. Hormone-dependent transcription from the MMTV promoter is repressed by osmotic stress when the promoter is integrated and has a normal chromatin structure. However, when the MMTV promoter is transiently transfected, the chromatin structure is less organized, and hormone induction is not affected by osmotic stress. On the integrated MMTV promoter, phosphorylation of histone H3 serine 10 and 28 increases in response to osmotic stress, but the transient promoter shows no change. Hormone-dependent glucocorticoid receptor binding is reduced on the repressed promoter, and elevated H3 phosphorylation is temporally correlated with maximal MMTV repression Additionally, the protein kinase C inhibitor rottlerin, but not other kinase inhibitors, blocks both histone H3 phosphorylation and osmotic repression of MMTV transcription. Glucocorticoid receptor binding is inversely correlated with H3 phosphorylation, suggesting that displacement of the glucocorticoid receptor from the promoter is due to H3 phosphorylation and is the mechanism for the osmotic repression of hormone-dependent transcription.
Highlights
Cells respond to changes in the environment by altering many cellular pathways and functions
This study investigated whether modification of histone H3 phosphorylation is a component of the osmotic stress response and/or required for the response of the mammary tumor virus (MMTV) promoter to osmotic stress
The osmotic stress response in human UL3 cells was verified by Western blots of p38, JNK, and ERK kinases that are phosphorylated in response to hypertonic stress in other cells
Summary
Cells respond to changes in the environment by altering many cellular pathways and functions. Hormone-dependent transcription from the MMTV promoter is repressed by osmotic stress when the promoter is integrated and has a normal chromatin structure. When the MMTV promoter is transiently transfected, the chromatin structure is less organized, and hormone induction is not affected by osmotic stress.
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