Constitutive c-Myb amino-terminal phosphorylation and DNA binding activity uncoupled during entry and passage through the cell cycle.

Abstract

The c-myb gene encodes a transcription factor that is central to hematopoietic cell growth. Phosphorylation of c-Myb by casein kinase 2 (CK2) at serines 11 and 12 has been variously implicated in the regulation of DNA binding. However, it is unclear when c-Myb phosphorylation at serines 11 and 12 occurs during the cell cycle and how this is regulated. We generated specific antisera that recognize phosphoserines 11 and 12 of c-Myb. C-Myb protein levels, extent of CK2 phosphorylation and DNA binding were then monitored following mitogenic stimulus and passage through the cell cycle in normal peripheral T-cells and the T leukemia cell line CCRF-CEM. We found that endogenous c-Myb is constitutively phosphorylated at serines 11 and 12. The amount of phosphorylated c-Myb correlates with DNA binding activity in cycling CEM cells but not upon entry of T-cells into the cell cycle. Exogenous expression of c-Myb with substitutions of serines 11 and 12 with glutamic acid or alanine had no effect on the transactivation of a c-Myb responsive reporter. These data strongly suggest that c-Myb is constitutively phosphorylated on serines 11 and 12 by CK2 or like activity and is not regulated during the cell cycle.

• Authors: A Cures, C House, C Kanei-Ishii, B Kemp, R G Ramsay
• Journal: Oncogene (Oncogene) Vol. 20 Issue 14 Pg. 1784-92 (Mar 29 2001) ISSN: 0950-9232 [Print] England
• PMID: 11313925 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Proto-Oncogene Proteins c-myb
• Serine
• DNA
• Casein Kinase II
• Protein Serine-Threonine Kinases

Topics

• Casein Kinase II
• Cell Cycle
• DNA (metabolism)
• Humans
• Phosphorylation
• Protein Serine-Threonine Kinases (physiology)
• Proto-Oncogene Proteins c-myb (metabolism)
• Serine (metabolism)
• Transcriptional Activation
• Tumor Cells, Cultured