Albert Einstein Cancer Center

Single-RNA counting reveals alternative modes of gene expression in yeast

Proper execution of transcriptional programs is a key requirement of gene expression regulation, demanding accurate control of timing and amplitude. How precisely the transcription machinery fulfills this task is not known. Using an in situ hybridization approach that detects single mRNA molecules, the Singer Laboratory measured mRNA abundance and transcriptional activity within single Saccharomyces cerevisiae cells. They found that expression levels for particular genes are higher than initially reported and can vary substantially among cells. However, variability for most constitutively expressed genes is unexpectedly small.  Low expression variation was shown to be achieved by transcribing genes using single transcription-initiation events that are clearly separated in time, rather than by transcriptional bursts. In contrast, PDR5, a gene regulated by the transcription coactivator complex SAGA, is expressed using transcription bursts, resulting in larger variation. This study directly demonstrated the existence of multiple expression modes used to modulate the transcriptome 

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