THE EFFECT OF PHYTOHEMAGGLUTININ ON RIBONUCLEIC ACID SYNTHESIS AND HISTONE ACETYLATION IN EQUINE LEUKOCYTES

Abstract

Equine granulo-cytes exposed to phytohemagglutinin [PHA] show a decreased capacity for RNA synthesis, unlike lymphocytes in which PHA stimulates RNA synthesis. The inhibited granulocytes also show a decrease in the rate of acetylation of arginine-rich histones. If the hlstones are acetylated under control conditions and the cells subsequently exposed to PHA, the acetyl groups are rapidly discarded, while amino acids Incorporated into the histone remain stable. Though these findings do not constitute a proof of a causal relationship between histone deacetylation and the inhibition of RNA synthesis, they do offer further support for the view that the functional state of the chromatin is reflected in patterns of histone acetylation.