A GROUP OF CHROMOSOMAL-PROTEINS IS SPECIFICALLY RELEASED BY SPERMINE AND LOSES DNA-BINDING ACTIVITY UPON PHOSPHORYLATION

Biologically relevant concentrations as low as 500 mu M spermine led t o the specific release of chromatin-associated proteins from nuclei of rice (Oryza sativa) seedlings. Using a southwestern technique, it was shown that several of these proteins bind DNA. This affinity was lost upon in organello phosphorylation by an endogenous kinase. The effect of spermine was very specific. Spermidine was far less effective and putrescine was essentially ineffective in releasing these proteins. Th e most abundant spermine-released protein was shown to be homologous t o the maize HMG1 protein. Our results suggest that spermine induces th e release of spermine-released proteins by changing DNA conformation. Binding of these proteins might be sensitive to long-range changes in chromosome structure caused by torsional stress.