Rapid Dephosphorylation of H1 Histones after Apoptosis Induction

Abstract

H1 histones are involved in the formation of higher order chromatin structures and in the modulation of gene expression. Changes in chromatin structure are a characteristic initial feature of apoptosis. We therefore have investigated the histone H1 pattern of the human leukemic cell line HL60 undergoing programmed cell death, as induced by topoisomerase I inhibition. Histone H1 proteins were isolated and analyzed by high performance liquid chromatography and capillary zone electrophoresis. DNA fragmentation after apoptosis induction was monitored by agarose gel electrophoresis. The patterns of the three H1 histone subtypes extractable from apoptotic HL60 cells significantly differed from those of control cells in showing a decrease of phosphorylated H1 subtypes and an increase of the respective dephosphorylated forms. This dephosphorylation of H1 histones could be observed already 45 min after apoptosis induction and preceded internucleosomal DNA cleavage by approximately 2 h. We conclude that during apoptotic DNA fragmentation, the H1 histones become rapidly dephosphorylated by a yet unknown protein phosphatase.

Hypoxia-induced and stress-specific changes in chromatin structure and function

“…However, cells treated with apoptosis-inducing agents, other than gliotoxin, do not undergo rapid phosphorylation of H3-S10 [111]. Likewise, dephosphorylation of H1 occurs during apoptosis, prior to internucleosomal cleavage, in contrast to phosphorylation of H1 observed during mitosis [112] Therefore, mitosis-associated chromatin condensation marks do not appear to be general markers of apoptosis.…”

H1 histone subtype constitution and phosphorylation state of the ageing cell system of human peripheral blood lymphocytes

“…The human leukemic cell line HL60 was cultured as previously described (Kratzmeier et al, 2000). Extraction of H1 histones from the HL60 cells was accomplished using perchloric acid in the same manner as that described for the lymphocytes.…”

“…The separation conditions are described in Kratzmeier et al (2000). Identification of the peaks was accomplished by mixing experiments using recombinantly-expressed H1 subtypes produced in our lab (see 2.6).…”

“…10 phase HPLC separation of the different subtypes was carried out as described by Kratzmeier et al (2000).…”

Caspase-mediated changes in histone H1 in early apoptosis: prolonged caspase activation in developing olfactory sensory neurons

“…[6][7][8] H1 undergoes alterations during apoptosis in vitro, including phosphorylation and poly(ADP)-ribosylation. [9][10][11] Once thought of as a static, nonparticipating structural element, H1 is now known to be a dynamic component of the machinery responsible for chromosomal events. Thus, H1 might be altered in the apoptotic process, making the chromosomal DNA vulnerable to cleavage.…”