Apoptotic DNA fragmentation is not related to the phosphorylation state of histone H1.
Changes in chromatin structure, histone phosphorylation and cleavage of DNA into nucleosome-size fragments are characteristic features of apoptosis. Since H1 histones bind to the site of DNA cleavage between nucleosomal cores, the question arises as to whether the state of H1 phosphorylation influences the rate of internucleosomal cleavage. Here, we tested the relation between DNA fragmentation and H1 phosphorylation both in cultured cells and in vitro. In Jurkat cells, hyperosmotic mannitol concentration resulted in apoptosis, including nucleosomal fragmentation, whereas apoptosis induction by increased NaCl concentration was not accompanied by DNA fragmentation. However, both treatments induced dephosphorylation of H1 histones. In contrast, treatment of Raji cells with alkylphosphocholine led to induction of apoptosis with internucleosomal fragmentation, albeit without notable histone H1 dephosphorylation. These results demonstrate that dephosphorylation of H1 histones is neither a prerequisite for nor a consequence of internucleosomal cleavage. Moreover, we observed with an in vitro assay that the known enhancing effect of H1 histones on the activity of the apoptosis-induced endonuclease DFF40 is independent of the subtype or the phosphorylation state of the linker histone.
Goebel
Wiebke
W
Institute for Biochemistry and Molecular Cell Biology, University of Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany.
Obermeyer
Natalie
N
Bleicher
Nadja
N
Kratzmeier
Martin
M
Eibl
Hans-Jörg
HJ
Doenecke
Detlef
D
Albig
Werner
W
D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D053938:DNA Fragmentation / Q000187:drug effects*; D003851:Deoxyribonucleases / Q000187:drug effects / Q000378:metabolism; D006657:Histones / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells / Q000187:drug effects; D009997:Osmotic Pressure; D010766:Phosphorylation; D000075223:Poly-ADP-Ribose Binding Proteins; D019311:Staurosporine / Q000494:pharmacology
D006657:Histones; D000075223:Poly-ADP-Ribose Binding Proteins; C113696:DFFB protein, human; D003851:Deoxyribonucleases; D019311:Staurosporine