Increased Phosphorylation of Histone H1 in Mouse Fibroblasts Transformed with Oncogenes or Constitutively Active Mitogen-activated Protein Kinase Kinase (*)
- Deborah N. Chadee(1)(2),
- William R. Taylor(1)(§),
- Robert A. R. Hurta(1),
- C. David Allis(3),
- Jim A. Wright(1)(2) and
- James R. Davie(2)(¶)
- From the (1)Manitoba Institute of Cell Biology, University of Manitoba, Winnipeg, Manitoba, R3E 0V9 Canada, the
- (2) Department of Biochemistry and Molecular Biology, University of Manitoba, Winnipeg, Manitoba, R3E OW3 Canada, and the
- (3) Department of Biology, Syracuse University, Syracuse, New York 13244-1270
- ¶To whom correspondence and reprint requests should be addressed: Dept. of Biochemistry and Molecular Biology, Faculty of Medicine, University of Manitoba, Winnipeg, MB, R3E OW3 Canada. Tel.: 204-789-3369; Fax: 204-783-0864.
Abstract
We compared the nucleosomal organization, histone H1 subtypes, and histone H1 phosphorylated isoforms of ras-transformed and parental 10T mouse fibroblasts. In agreement with previous studies, we found that ras-transformed mouse fibroblasts have a less condensed chromatin structure than normal fibroblasts. ras-transformed and parental 10T cells had similar amounts of H1 subtypes, proteins that have a key role in the compaction of
chromatin. However, labeling studies with 
P and Western blot experiments with an antiphosphorylated H1 antibody show that interphase ras-transformed cells have higher levels of phosphorylated H1 isoforms than parental cells. G1/S phase-arrested ras-transformed cells had higher amounts of phosphorylated H1 than G1/S phase-arrested parental cells. Mouse fibroblasts transformed with fes, mos, raf, myc, or constitutively active mitogen-activated protein (MAP) kinase kinase had increased levels of phosphorylated H1. These
observations suggest that increased phosphorylation of H1 is one of the consequences of the persistent activation of the mitogen-activated
protein kinase signal transduction pathway. Indirect immunofluorescent studies show that phosphorylated H1b is localized in
centers of RNA splicing in the nucleus, suggesting that this modified H1 subtype is complexed to transcriptionally active
chromatin.
Footnotes
-
↵* This work was supported by Grant MA-12283 from the Medical Research Council of Canada (to J. A. W. and J. R. D.) and by Public Health Service Grant GM 40922 from the National Institutes of Health (to C. D. A.). The award of a Cancer Research Society, Inc. Studentship (to W. R. T.), a National Cancer Institute of Canada Terry Fox Senior Scientist (to J. A. W.) and a Medical Research Council Scientist (to J. R. D.) are also gratefully acknowledged. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are;
- MAP
-
mitogen-activated protein
- PMSF
-
phenylmethylsulfonyl fluoride
- PIPES
-
1,4-piperazinediethanesulfonic acid.
-
↵2 D. N. Chadee, W. R. Taylor, R. A. R. Hurta, C. D. Allis, J. A. Wright, and J. R. Davie, unpublished observations.
-
- Received May 10, 1995.
- Revision received June 12, 1995.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
