Rabbit Anti-Human HMG14 (Phospho Ser20/24) Polyclonal antibody

The RAS-mitogen-activated protein kinase signaling pathway is often deregulated in cancer cells. In metastatic HRAS-transformed mouse fibroblasts (Ciras-3), the RAS-MAPK pathway is constitutively activated. We show here that Ciras-3 cells exhibit a higher incidence of chromosomal instability than 10T1/2 cells, including higher levels of clonal and nonclonal chromosomal aberrations. Stimulation of serum starved 10T1/2 and Ciras-3 cells with phorbol esters (TPA) results in the phosphorylation of histone H3 at serine 10 and serine 28. Regardless of the increased genomic instability in Ciras-3 cells, TPA-induced H3 phosphorylated at serine 10 and H3 phosphorylated at serine 28 partitioned into distinct nuclear subdomains as they did in the parental cells. However, the timing of the response of the H3 phosphorylation event to TPA induction was delayed in Ciras-3 cells. Further Ciras-3 cells, which have a more open chromatin structure, had increased steady state levels of phosphorylated H3 and HMGN1 relative to parental 10T1/2 cells. TPA-induced H3 phosphorylated at serine 10 and 28 were colocalized with the transcriptionally initiated form of RNA polymerase II in 10T1/2 and Ciras-3 cells. Chromatin immunoprecipitation assays demonstrated that TPA-induced H3 phosphorylation at serine 28 was associated with the immediate early JUN promoter, providing direct evidence that this histone post-translational modification is associated with transcriptionally active genes. Together our results demonstrate the increased genomic instability and alterations in the epigenetic program in HRAS-transformed cells. (C) 2009 Wiley-Liss, Inc.

We report that loss of HMGN1, a nucleosome-binding protein that alters the compaction of the chromatin fiber, increases the cellular sensitivity to ionizing radiation and the tumor burden of mice. The mortality and tumor burden of ionizing radiation-treated Hmgn1(-/-) mice is higher than that of their Hmgn1(+/+) littermates. Hmgn1(-/-) fibroblasts have an altered G(2)-M checkpoint activation and are hypersensitive to ionizing radiation. The ionizing radiation hypersensitivity and the aberrant G(2)-M checkpoint activation of Hmgn1(-/-) fibroblasts can be reverted by transfections with plasmids expressing wild-type HMGN1, but not with plasmids expressing mutant HMGN proteins that do not bind to chromatin. Transformed Hmgn1(-/-) fibroblasts grow in soft agar and produce tumors in nude mice with a significantly higher efficiency than Hmgn1(+/+) fibroblasts, suggesting that loss of HMGN1 protein disrupts cellular events controlling proliferation and growth. Hingn1(-/-) mice have a higher incidence of multiple malignant tumors and metastases than their Hmgn1(+/+) littermates. We suggest that HMGN1 optimizes the cellular response to ionizing radiation and to other tumorigenic events; therefore, loss of this protein increases the tumor burden in mice.