Zusammenfassung:Ehrlich-Ascites-Tumorzellen wurden in vitro mit [ 3 H]Methionin inkubiert, und der Radioaktivitätseinbau in einzelne gelelektrophoretisch trennbare Histonfraktionen untersucht. Die jeweiligen Histongruppen zeigten unterschiedliche Methionin-und Methyllysin-Radioaktivitäten, während die Unterfraktionen einer Gruppe sich gleich verhielten. Ebenso war das Verhältnis von Mono-zu Di-zu Trimethyllysin in den Unterfraktionen gleich, während es sich von Histongruppe zu -gruppe unterschied. Es ergaben sich Hinweise darauf, daß die Höhermethylierung bis zum Trimethyllysin nicht auf einmal, sondern schrittweise erfolgt. Im Chase-Experiment war kein Abfall der Methyllysin-Radioaktivität über eine Zeitdauer von 3 h zu verzeichnen, was bedeutet, daß kein rascher Methylgruppen-Turnover stattfindet. Relative stability of lysine-bound methyl groups in arginine-rich histones and their subffactions of Ehrlich ascites tumor cells in vitroSummary: Ehrlich ascites tumor cells were incubated /// vitro with [ 3 H]methionine, and the labelling of different histones and their subfractions, which can be separated on very long gels by analytical gel electrophoresis, was examined. The various histone groups showed different methionine and methyllysine radioactivities, while the bands of one group incorporated nearly identical radioactivities. The ratio of mono-to di-to trimethyllysine in the bands of one group was identical as well, but different from one group to another. There were indications that the methyl labelling from mono-to di-and trimethyllysine at one histone site occurred not at once but stepwise. In chase experiments no decrease of methyllysine activity could be observed over a period of 3 h, which means that no rapid methyl group turnover occurs.

An immunological cross-reaction between histones and the encephalitogenic myelin basic protein (MBP) of brain white matter has been discussed repeatedly. The binding ability of the histones Fl, F2a1, F2a2, F2b and F3, isolated from calf thymus, and of the F2c fraction of chicken erythrocytes to antibodies against human MBP was examined using a radioimmunological technique with high sensitivity. There was no evidence for any immunological cross-reaction between these closely related basic proteins, neither by the direct binding test of labelled histones to the antibodies to MBP, nor by the binding inhibition test of MBP to its antibodies in presence of excessive amounts of histones.