Changes in histone gene dosage alter transcription in yeast

Chromatin structure is believed to be important for a number of cellular processes, including transcription. However, the role of nucleosomes in transcription is not well understood. We have identified the yeast histone locus HTB1-HTB1, encoding histones H2A and H2B, as a suppressor of solo delta insertion mutations that inhibit adjacent gene expression. The HTA1-HTB1 locus causes suppression either when present on a high-copy-number plasmid or when mutant. These changes in HTA1-HTB1 after transcription of the genes adjacent to the delta insertions. On the basis of this result, we have examined the effects of increased and decreased histone gene dosage for all four yeast histone loci. From the types of histone gene dosage changes that cause suppression of insertion mutations, we conclude that altered stoichiometry of histone dimer sets can alter transcription in yeast.