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Overlapping coactivator function is required for transcriptional activation by the Candida glabrata Pdr1 transcription factor
Journal article   Open access   Peer reviewed

Overlapping coactivator function is required for transcriptional activation by the Candida glabrata Pdr1 transcription factor

Thomas P Conway, Lucia Simonicova and W Scott Moye-Rowley
Genetics (Austin), Vol.228(1), iyae115
07/19/2024
DOI: 10.1093/genetics/iyae115
PMCID: PMC11791784
PMID: 39028831
Appears in  UI Libraries Support Open Access
url
https://doi.org/10.1093/genetics/iyae115View
Published (Version of record) Open Access

Abstract

Azole resistance in the pathogenic yeast Candida glabrata is a serious clinical complication and increasing in frequency. The majority of resistant organisms have been found to contain a substitution mutation in the Zn2Cys6 zinc cluster-containing transcription factor Pdr1. These mutations typically lead to this factor driving high, constitutive expression of target genes like the ATP-binding cassette transporter-encoding gene CDR1. Overexpression of Cdr1 is required for the observed elevated fluconazole resistance exhibited by strains containing one of these hyperactive PDR1 alleles. While the identity of hyperactive PDR1 alleles has been extensively documented, the mechanisms underlying how these gain-of-function (GOF) forms of Pdr1 lead to elevated target gene transcription are not well understood. We have used a tandem affinity purification (TAP)-tagged form of Pdr1 to identify coactivator proteins that biochemically purify with the wild-type and two different GOF forms of Pdr1. Three coactivator proteins were found to associate with Pdr1: the SWI/SNF complex Snf2 chromatin remodeling protein and two different components of the SAGA complex, Spt7 and Ngg1. We found that deletion mutants lacking either SNF2 or SPT7 exhibited growth defects, even in the absence of fluconazole challenge. To overcome these issues, we employed a conditional degradation system to acutely deplete these coactivators and determined that loss of either coactivator complex, SWI/SNF or SAGA, caused defects in Pdr1-dependent transcription. A double degron strain that could be depleted for both SWI/SNF and SAGA exhibited a profound defect in PDR1 autoregulation, revealing that these complexes work together to ensure high level Pdr1-dependent gene transcription.Azole resistance in the pathogenic yeast Candida glabrata is a serious clinical complication and increasing in frequency. The majority of resistant organisms have been found to contain a substitution mutation in the Zn2Cys6 zinc cluster-containing transcription factor Pdr1. These mutations typically lead to this factor driving high, constitutive expression of target genes like the ATP-binding cassette transporter-encoding gene CDR1. Overexpression of Cdr1 is required for the observed elevated fluconazole resistance exhibited by strains containing one of these hyperactive PDR1 alleles. While the identity of hyperactive PDR1 alleles has been extensively documented, the mechanisms underlying how these gain-of-function (GOF) forms of Pdr1 lead to elevated target gene transcription are not well understood. We have used a tandem affinity purification (TAP)-tagged form of Pdr1 to identify coactivator proteins that biochemically purify with the wild-type and two different GOF forms of Pdr1. Three coactivator proteins were found to associate with Pdr1: the SWI/SNF complex Snf2 chromatin remodeling protein and two different components of the SAGA complex, Spt7 and Ngg1. We found that deletion mutants lacking either SNF2 or SPT7 exhibited growth defects, even in the absence of fluconazole challenge. To overcome these issues, we employed a conditional degradation system to acutely deplete these coactivators and determined that loss of either coactivator complex, SWI/SNF or SAGA, caused defects in Pdr1-dependent transcription. A double degron strain that could be depleted for both SWI/SNF and SAGA exhibited a profound defect in PDR1 autoregulation, revealing that these complexes work together to ensure high level Pdr1-dependent gene transcription.
 Drug Resistance Transcription Candida glabrata pathogenic yeast UIOWA OA Agreement

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