Differential inhibition of histone and polyamine acetylases by multisubstrate analogues

Mammalian cells contain a number of enzymes catalyzing the acetylation of polyamines and histones including an inducible spermidine/spermine N1-acetyltransferase which may play a key role in regulating the interconversion of polyamines [Matsui, I., Wiegand, L., & Pegg, A. E. (1981) J. Biol. Chem. 256, 2454-2459]. The present experiments were carried out in order to provide a method to distinguish this enzyme from other polyamine/histone acetylases and to test whether specific inhibitors of its activity could be obtained. Rabbit antiserum to homogeneous rat liver spermidine/spermine N1-acetyltransferase had no effect on the activity of a crude nuclear extract from rat liver, indicating that its spermidine acetylating capability is not related to the cytosolic spermidine/spermine N1-acetyltransferase induced by hepatotoxins. Potential multisubstrate analogues were prepared by attaching various polyamines to coenzyme A via an acetic acid linkage and tested as potential inhibitors of the acetylation of spermidine and histones. There was little difference in the potency of these polyamine derivatives as inhibitors of histone or spermidine acetylation by the crude nuclear extracts which appeared to contain at least two such activities, one inhibited completely by 20-30 microM and the other amounting to 50% of the total being unaffected by 100 microM. Spermidine/spermine N1-acetyltransferase was also inhibited by all the derivatives, but the potency toward this enzyme differed widely. The derivative from sym-norspermidine was a very strong inhibitor, giving 50% inhibition at 0.3 microM, and was more than 1 order of magnitude more active than the others.(ABSTRACT TRUNCATED AT 250 WORDS)