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Curr Biol. 2017 Dec 4;27(23):3591-3602.e3. doi: 10.1016/j.cub.2017.10.035. Epub 2017 Nov 16.

Genetic and Epigenetic Strategies Potentiate Gal4 Activation to Enhance Fitness in Recently Diverged Yeast Species.

Author information

1
Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA.
2
Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA. Electronic address: j-brickner@northwestern.edu.

Abstract

Certain genes show more rapid reactivation for several generations following repression, a conserved phenomenon called epigenetic transcriptional memory. Following previous growth in galactose, GAL gene transcriptional memory confers a strong fitness benefit in Saccharomyces cerevisiae adapting to growth in galactose for up to 8 generations. A genetic screen for mutants defective for GAL gene memory revealed new insights into the molecular mechanism, adaptive consequences, and evolutionary history of memory. A point mutation in the Gal1 co-activator that disrupts the interaction with the Gal80 inhibitor specifically and completely disrupted memory. This mutation confirms that cytoplasmically inherited Gal1 produced during previous growth in galactose directly interferes with Gal80 repression to promote faster induction of GAL genes. This mitotically heritable mode of regulation is recently evolved; in a diverged Saccharomyces species, GAL genes show constitutively faster activation due to genetically encoded basal expression of Gal1. Thus, recently diverged species utilize either epigenetic or genetic strategies to regulate the same molecular mechanism. The screen also revealed that the central domain of the Gal4 transcription factor both regulates the stochasticity of GAL gene expression and potentiates stronger GAL gene activation in the presence of Gal1. The central domain is critical for GAL gene transcriptional memory; Gal4 lacking the central domain fails to potentiate GAL gene expression and is unresponsive to previous Gal1 expression.

KEYWORDS:

GAL genes; adaptive fitness; epigenetics; evolution; stochastic expression; trade-offs; transcriptional activation; transcriptional memory; transcriptional potentiation

PMID:
29153325
PMCID:
PMC5846685
[Available on 2018-12-04]
DOI:
10.1016/j.cub.2017.10.035
[Indexed for MEDLINE]

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