title: Molecular characterization of the Aspergillus nidulans fbxA encoding an F-box protein involved in xylanase induction.
abstract: The filamentous fungus Aspergillus nidulans has been used as a fungal model system to study the regulation of xylanase production. These genes are activated at transcriptional level by the master regulator the transcriptional factor XlnR and repressed by carbon catabolite repression (CCR) mediated by the wide-domain repressor CreA. Here, we screened a collection of 42 A. nidulans F-box deletion mutants grown either in xylose or xylan as the single carbon source in the presence of the glucose analog 2-deoxy-D-glucose, aiming to identify mutants that have deregulated xylanase induction. We were able to recognize a null mutant in a gene (fbxA) that has decreased xylanase activity and reduced xlnA and xlnD mRNA accumulation. The ΔfbxA mutant interacts genetically with creAd-30, creB15, and creC27 mutants. FbxA is a novel protein containing a functional F-box domain that binds to Skp1 from the SCF-type ligase. Blastp analysis suggested that FbxA is a protein exclusive from fungi, without any apparent homologs in higher eukaryotes. Our work emphasizes the importance of the ubiquitination in the A. nidulans xylanase induction and CCR. The identification of FbxA provides another layer of complexity to xylanase induction and CCR phenomena in filamentous fungi.
authors.affiliation: Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Ana Cristina
authors.initials: AC
authors.lastname: Colabardini
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: Humanes
authors.forename: Paula Fagundes
authors.initials: PF
authors.lastname: Gouvea
authors.forename: Marcela
authors.initials: M
authors.lastname: Savoldi
authors.forename: Maria Helena S
authors.initials: MH
authors.lastname: Goldman
authors.forename: Marcia Regina von Zeska
authors.initials: MR
authors.lastname: Kress
authors.forename: Özgür
authors.initials: Ö
authors.lastname: Bayram
authors.forename: Juliana Velasco de Castro
authors.initials: JV
authors.lastname: Oliveira
authors.forename: Marcelo Damário
authors.initials: MD
authors.lastname: Gomes
authors.forename: Gerhard H
authors.initials: GH
authors.lastname: Braus
authors.forename: Gustavo Henrique
authors.initials: GH
authors.lastname: Goldman
mesh_terms: D001233:Aspergillus nidulans / Q000235:genetics* / Q000378:metabolism*; D057465:Catabolite Repression / Q000235:genetics*; D003847:Deoxyglucose / Q000378:metabolism; D043364:Endo-1,4-beta Xylanases / Q000235:genetics / Q000378:metabolism; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D014990:Xylans / Q000378:metabolism; D014994:Xylose / Q000378:metabolism
chemical_list: D044783:F-Box Proteins; D005656:Fungal Proteins; D044786:S-Phase Kinase-Associated Proteins; D015534:Trans-Activators; C115443:XlnR protein, Aspergillus; D014990:Xylans; D003847:Deoxyglucose; D014994:Xylose; D043364:Endo-1,4-beta Xylanases