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Toxins 2012, 4(12), 1582-1600; doi:10.3390/toxins4121582
Article

Association with AflR in Endosomes Reveals New Functions for AflJ in Aflatoxin Biosynthesis

1,* , 1
, 1
, 1
, 2
, 3
, 1
, 1
 and 2
1 Southern Regional Research Center, Agricultural Research Service/United States Department of Agriculture, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA 2 Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 488244, USA 3 Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 488244, USA
* Author to whom correspondence should be addressed.
Received: 19 November 2012 / Revised: 5 December 2012 / Accepted: 12 December 2012 / Published: 19 December 2012
(This article belongs to the Special Issue Mycotoxins in Food and Feed)
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Abstract

Aflatoxins are the most potent naturally occurring carcinogens of fungal origin. Biosynthesis of aflatoxin involves the coordinated expression of more than 25 genes. The function of one gene in the aflatoxin gene cluster, aflJ, is not entirely understood but, because previous studies demonstrated a physical interaction between the Zn2Cys6 transcription factor AflR and AflJ, AflJ was proposed to act as a transcriptional co-activator. Image analysis revealed that, in the absence of aflJ in A. parasiticus, endosomes cluster within cells and near septa. AflJ fused to yellow fluorescent protein complemented the mutation in A. parasiticus ΔaflJ and localized mainly in endosomes. We found that AflJ co-localizes with AflR both in endosomes and in nuclei. Chromatin immunoprecipitation did not detect AflJ binding at known AflR DNA recognition sites suggesting that AflJ either does not bind to these sites or binds to them transiently. Based on these data, we hypothesize that AflJ assists in AflR transport to or from the nucleus, thus controlling the availability of AflR for transcriptional activation of aflatoxin biosynthesis cluster genes. AflJ may also assist in directing endosomes to the cytoplasmic membrane for aflatoxin export.
Keywords: aflatoxin; protein trafficking; Aspergillus parasiticus; aflatoxin; aflatoxisomes; endosomes; AflJ; AflR aflatoxin; protein trafficking; Aspergillus parasiticus; aflatoxin; aflatoxisomes; endosomes; AflJ; AflR
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Ehrlich, K.C.; Mack, B.M.; Wei, Q.; Li, P.; Roze, L.V.; Dazzo, F.; Cary, J.W.; Bhatnagar, D.; Linz, J.E. Association with AflR in Endosomes Reveals New Functions for AflJ in Aflatoxin Biosynthesis. Toxins 2012, 4, 1582-1600.

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