+ Site Statistics
+ Search Articles
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ PDF Full Text
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Translate
+ Recently Requested

Sterol Biosynthesis and Azole Tolerance Is Governed by the Opposing Actions of SrbA and the CCAAT Binding Complex

Sterol Biosynthesis and Azole Tolerance Is Governed by the Opposing Actions of SrbA and the CCAAT Binding Complex

Plos Pathogens 12(7): E1005775

Azole drugs selectively target fungal sterol biosynthesis and are critical to our antifungal therapeutic arsenal. However, resistance to this class of drugs, particularly in the major human mould pathogen Aspergillus fumigatus, is emerging and reaching levels that have prompted some to suggest that there is a realistic probability that they will be lost for clinical use. The dominating class of pan-azole resistant isolates is characterized by the presence of a tandem repeat of at least 34 bases (TR34) within the promoter of cyp51A, the gene encoding the azole drug target sterol C14-demethylase. Here we demonstrate that the repeat sequence in TR34 is bound by both the sterol regulatory element binding protein (SREBP) SrbA, and the CCAAT binding complex (CBC). We show that the CBC acts complementary to SrbA as a negative regulator of ergosterol biosynthesis and show that lack of CBC activity results in increased sterol levels via transcriptional derepression of multiple ergosterol biosynthetic genes including those coding for HMG-CoA-synthase, HMG-CoA-reductase and sterol C14-demethylase. In agreement with these findings, inactivation of the CBC increased tolerance to different classes of drugs targeting ergosterol biosynthesis including the azoles, allylamines (terbinafine) and statins (simvastatin). We reveal that a clinically relevant mutation in HapE (P88L) significantly impairs the binding affinity of the CBC to its target site. We identify that the mechanism underpinning TR34 driven overexpression of cyp51A results from duplication of SrbA but not CBC binding sites and show that deletion of the 34 mer results in lack of cyp51A expression and increased azole susceptibility similar to a cyp51A null mutant. Finally we show that strains lacking a functional CBC are severely attenuated for pathogenicity in a pulmonary and systemic model of aspergillosis.

(PDF emailed within 1 workday: $29.90)

Accession: 058905061

Download citation: RISBibTeXText

PMID: 27438727

Related references

Damage resistance protein (Dap) contributes to azole resistance in a sterol-regulatory-element-binding protein SrbA-dependent way. Applied Microbiology and Biotechnology 101(9): 3729-3741, 2017

Structural analyses of Candida albicans sterol 14α-demethylase complexed with azole drugs address the molecular basis of azole-mediated inhibition of fungal sterol biosynthesis. Journal of Biological Chemistry 292(16): 6728-6743, 2017

Terminating hepatocyte proliferation during liver regeneration: the roles of two members of the same family (CCAAT-enhancer-binding protein alpha and beta) with opposing actions. Hepatology 61(1): 32-34, 2015

Sterol uptake and sterol biosynthesis act coordinately to mediate antifungal resistance in Candida glabrata under azole and hypoxic stress. Molecular Medicine Reports 17(5): 6585-6597, 2018

Sterol regulation of 3-hydroxy-3-methylglutaryl-coenzyme A synthase gene through a direct interaction between sterol regulatory element binding protein and the trimeric CCAAT-binding factor/nuclear factor Y. Journal of Biological Chemistry 273(3): 1349-1356, 1998

Azole sterol biosynthesis inhibitors as anti mycobacterial agents. Biochemical Society Transactions 29(1): A30.1-A30, 2001

Sterol biosynthesis inhibiting piperazine, pyridine, pyrimidine and azole fungicides. Modern selective fungicides: properties applications mechanisms of action editor H Lyr in cooperation with H Buchenhaueretal: 204, 1987

Multidrug Transporters and Alterations in Sterol Biosynthesis Contribute to Azole Antifungal Resistance in Candida parapsilosis. Antimicrobial Agents and ChemoTherapy 59(10): 5942-5950, 2016

Overexpression of Brassica juncea wild-type and mutant HMG-CoA synthase 1 in Arabidopsis up-regulates genes in sterol biosynthesis and enhances sterol production and stress tolerance. Plant Biotechnology Journal 10(1): 31-42, 2012

Defective sterol C5-6 desaturation and azole resistance: a new hypothesis for the mode of action of azole antifungals. Biochemical and Biophysical Research Communications 164(3): 1170-1175, 1989

Azole binding properties of Candida albicans sterol 14-alpha demethylase (CaCYP51). Antimicrobial Agents and ChemoTherapy 54(10): 4235-4245, 2011

Novel basic-region helix-loop-helix transcription factor (AnBH1) of Aspergillus nidulans counteracts the CCAAT-binding complex AnCF in the promoter of a penicillin biosynthesis gene. Journal of Molecular Biology 323(3): 425-439, 2002

Crystal structure of cytochrome P450 14a-sterol demethylase (CYP51) from Mycobacterium tuberculosis in complex with azole inhibitors. Proceedings of the National Academy of Sciences of the United States of America 98(6): 68-73, 2001

HIV protease inhibitor induces fatty acid and sterol biosynthesis in liver and adipose tissues due to the accumulation of activated sterol regulatory element-binding proteins in the nucleus. Journal of Biological Chemistry 276(40): 37514-9, 2001

Functional characterization of the human resistin promoter with adipocyte determination- and differentiation-dependent factor 1/sterol regulatory element binding protein 1c and CCAAT enhancer binding protein-alpha. Molecular Endocrinology 17(8): 1522-1533, 2003