Isolation and characterisation of suppressors of conditional histone mutants

Abstract

Histone H4 is one of four core histone proteins that make up the nucleosome, the smallest building block of chromosomes. Alanine-scanning mutagenesis of histone H4 had determined that the three mutant proteins H4Y51A, H4E53A and H4Y98A conferred sensitivity to 3-aminotriazole (AT), antimycin A and high temperature when expressed in place of endogenous histone H4. Multi-copy phenotypic suppressor screens were performed and the histone acetyltransferases Gcn5, Hpa1 and Hpa2 were isolated as multi-copy suppressors of the AT sensitivity of the H4Y98A mutant strain. Chromatin immunoprecipitation studies carried out at the HIS3 gene showed that the histidine starvation-induced histone eviction was reduced in the H4Y98A mutant strain and restored back to the WT levels upon the over-expression of Gcn5. By controlling all aspects of DNA biology, histones play an important role in human diseases, and the homologous human proteins of the isolated suppressors might become interesting drug targets in the future.