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Nucleosome Positioning and Histone H3 Acetylation Are Independent Processes in the Aspergillus nidulans prnD-prnB Bidirectional Promoter ^,

Yazmid Reyes-Dominguez,^1,2 Frank Narendja,^1, Harald Berger,¹ Andreas Gallmetzer,¹ Rafael Fernandez-Martin,^2, Irene Garcia,^2,¶ Claudio Scazzocchio,^2,# and Joseph Strauss^1*

Fungal Genomics Unit, Austrian Research Centers and BOKU Vienna, A-1190 Vienna, Austria,¹ Istitute de Genetique et Microbiologie, Université Paris-Sud, F-91495 Orsay-CEDEX, France²

Received 22 May 2007/ Accepted 7 February 2008

In Aspergillus nidulans, proline can be used as a carbon and nitrogen source, and its metabolism requires the integration of three signals, including proline induction and nitrogen and carbon metabolite derepression. We have previously shown that the bidirectional promoter in the prnD-prnB intergenic region undergoes drastic chromatin rearrangements such that proline induction leads to the loss of positioned nucleosomes, whereas simultaneous carbon and nitrogen metabolite repression results in the partial repositioning of these nucleosomes. In the proline cluster, the inhibition of deacetylases by trichostatin A leads to partial derepression and is associated with a lack of nucleosome positioning. Here, we investigate the effect of histone acetylation in the proline cluster using strains deleted of essential components of putative A. nidulans histone acetyltransferase complexes, namely, gcnE and adaB, the orthologues of the Saccharomyces cerevisiae GCN5 and ADA2 genes, respectively. Surprisingly, GcnE and AdaB are not required for transcriptional activation and chromatin remodeling but are required for the repression of prnB and prnD and for the repositioning of nucleosomes in the divergent promoter region. Chromatin immunoprecipitation directed against histone H3 lysines K9 and K14 revealed that GcnE and AdaB participate in increasing the acetylation level of at least one nucleosome in the prnD-prnB intergenic region during activation, but these activities do not determine nucleosome positioning. Our results are consistent with a function of GcnE and AdaB in gene repression of the proline cluster, probably an indirect effect related to the function of CreA, the DNA-binding protein mediating carbon catabolite repression in A. nidulans.

Published ahead of print on 22 February 2008.

Supplemental material for this article may be found at http://ec.asm.org/.

Present address: Federal Environment Agency, Umweltbundesamt GesmbH, Spittelauerlände 5, A-1090 Vienna, Austria.

Present address: Laboratorio Biotecnología Animal, Universidad de Buenos Aires, Avenida San Martin 4453, Capital Federal, Argentina.

^¶ Present address: Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC-Universidad de Sevilla, Américo Vespucio, 49, 41092-Sevilla, Spain.

^# Present address: Department of Microbiology, Imperial College, London, Flowers Building, Armstrong Road, London SW7 2AZ, United Kingdom.