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Antimicrobial Agents and Chemotherapy, April 2008, p. 1481-1492, Vol. 52, No. 4
0066-4804/08/$08.00+0     doi:10.1128/AAC.01106-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Transcriptional Activation and Increased mRNA Stability Contribute to Overexpression of CDR1 in Azole-Resistant Candida albicans{triangledown}

Raman Manoharlal,1 Naseem Akhtar Gaur,1,{dagger} Sneh Lata Panwar,2 Joachim Morschhäuser,3 and Rajendra Prasad1*

Membrane Biology,1 Yeast Molecular Genetics Laboratories, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India,2 Institut für Molekulare Infektionsbiologie, Universität Würzburg, Röntgenring 11, D-97070 Würzburg, Germany3

Received 22 August 2007/ Returned for modification 23 September 2007/ Accepted 2 February 2008

Many azole-resistant (AR) clinical isolates of Candida albicans display increased expression of the drug transporters CDR1 and CDR2. In this study, we evaluate the molecular mechanisms that contribute to the maintenance of constitutively high CDR1 transcript levels in two matched pairs of azole-susceptible (AS) and AR clinical isolates of C. albicans. To address this, we use reporter constructs of GFP and lacZ fused either to the CDR1 promoter (PCDR1-GFP/lacZ; transcriptional fusion) or to the CDR1 open reading frame (PCDR1-CDR1-GFP/lacZ; translational fusion) integrated at the native CDR1 locus. It is observed that expression of the two reporter genes as a transcriptional fusion in the AR isolates is higher than that in matched AS isolates. However, the difference in the reporter activity between the AS and AR isolates is even greater for the translational fusions, indicating that the sequences within the CDR1 coding region also contribute to its increased expression in AR isolates. Further analysis of these observations by transcription run-on assays demonstrated a ~5- to 7-fold difference in the transcription initiation rates for the AR isolates from those for their respective matched AS isolates. Measurement of mRNA stability showed that the half-life of CDR1 mRNA in the AR isolates was threefold higher than that in the corresponding AS isolates. Our results demonstrate that both increased CDR1 transcription and enhanced CDR1 mRNA stability contribute to the overexpression of CDR1 in AR C. albicans isolates.

* Corresponding author. Mailing address: Jawaharlal Nehru University, School of Life Sciences, JNU Campus, New Mehrauli Road, New Delhi 110067, India. Phone: 91-11-26704509. Fax: 011-91-11-26187338. E-mail: rp47jnu{at}gmail.com or rp47{at}mail.jnu.ac.in

{triangledown} Published ahead of print on 11 February 2008.

{dagger} Present address: Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892.

Antimicrobial Agents and Chemotherapy, April 2008, p. 1481-1492, Vol. 52, No. 4
0066-4804/08/$08.00+0     doi:10.1128/AAC.01106-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Holmes, A. R., Lin, Y.-H., Niimi, K., Lamping, E., Keniya, M., Niimi, M., Tanabe, K., Monk, B. C., Cannon, R. D. (2008). ABC Transporter Cdr1p Contributes More than Cdr2p Does to Fluconazole Efflux in Fluconazole-Resistant Candida albicans Clinical Isolates. Antimicrob. Agents Chemother. 52: 3851-3862 [Abstract] [Full Text]  


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