Yeast histone genes show dosage compensation.

The copy number of yeast histone genes was increased by inserting an extra H2A,H2B gene pair into the haploid genome by the technique of yeast transformation. The presence of this extra gene copy has no detectable effect on cell growth. The steady-state levels of histone H2A,H2B mRNAs are not elevated in transformed strains, and they correspond to the levels measured for the parental strain. The transcription rate is increased in these strains, however, and the parental steady-state levels of histone mRNAs are maintained by increased turnover of histone transcripts. These results demonstrate that yeast histone genes display dosage compensation through the operation of posttranscriptional controls. They also suggest that maintainance of a constant ratio between histone mRNA concentration and the rate of chromosome replication may be of general importance to histone mRNA metabolism.