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Type: Journal article
Title: The CreB deubiquitinating enzyme does not directly target the CreA repressor protein in Aspergillus nidulans
Author: Alam, M.
Kamlangdee, N.
Kelly, J.
Citation: Current Genetics: lower eukaryotes and organelles, 2017; 63(4):647-667
Publisher: Springer-Verlag
Issue Date: 2017
ISSN: 0172-8083
Statement of
Md Ashiqul Alam, Niyom Kamlangdee, Joan M. Kelly
Abstract: Ubiquitination/deubiquitination pathways are now recognized as key components of gene regulatory mechanisms in eukaryotes. The major transcriptional repressor for carbon catabolite repression in Aspergillus nidulans is CreA, and mutational analysis led to the suggestion that a regulatory ubiquitination/deubiquitination pathway is involved. A key unanswered question is if and how this pathway, comprising CreB (deubiquitinating enzyme) and HulA (ubiquitin ligase) and other proteins, is involved in the regulatory mechanism. Previously, missense alleles of creA and creB were analysed for genetic interactions, and here we extended this to complete loss-of-function alleles of creA and creB, and compared morphological and biochemical phenotypes, which confirmed genetic interaction between the genes. We investigated whether CreA, or a protein in a complex with it, is a direct target of the CreB deubiquitination enzyme, using co-purifications of CreA and CreB, first using strains that overexpress the proteins and then using strains that express the proteins from their native promoters. The Phos-tag system was used to show that CreA is a phosphorylated protein, but no ubiquitination was detected using anti-ubiquitin antibodies and Western analysis. These findings were confirmed using mass spectrometry, which confirmed that CreA was differentially phosphorylated but not ubiquitinated. Thus, CreA is not a direct target of CreB, and nor are proteins that form part of a stable complex with CreA a target of CreB. These results open up new questions regarding the molecular mechanism of CreA repressing activity, and how the ubiquitination pathway involving CreB interacts with this regulatory network.
Keywords: Regulatory deubiquitination; Transcriptional repression; CreA DNA-binding protein; CreB deubiquitinating enzyme; Aspergillus nidulans; Carbon catabolite repression
Description: First Online: 23 November 2016
Rights: © Springer-Verlag Berlin Heidelberg 2016
DOI: 10.1007/s00294-016-0666-3
Appears in Collections:Aurora harvest 3
Molecular and Biomedical Science publications

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