Activation of aflatoxin B1 by expression of human CYP1A2 polymorphisms in Saccharomyces cerevisiae

A feeding trial (35 days) was carried out to investigate the effect of Saccharomyces cerevisiae cell wall as a mycotoxin biodegradation agent on the performance, feed efficiency, carcass traits, and immunity response against diseases in broilers fed aflatoxin B1 contaminated diets. For this purpose, 200 one day old broilers were randomly allotted into four groups, each with five replicates (10 birds per replicate). Four starter and finisher experimental rations were formulated by using (A) 0, (B) 1.25, (C) 2.5, and (D) 3.75 g kg−1 of Saccharomyces cerevisiae. Experimental diets were contaminated with aflatoxin B1 (100 ppb kg−1 diet). The experimental chicks were kept under standard managerial conditions, and the vaccination program was followed against infectious bursal disease (IBD), infectious bronchitis (IB), and Newcastle disease (ND) diseases. At the end of the feeding trial, carcass, organ weight, and blood samples were collected randomly to determine the carcass traits and antibody titer against ND and IBD viruses. Throughout the experiment, the addition of 3.75 g kg−1 of the Saccharomyces cerevisiae cell wall (Group-D) in feed resulted in the highest weight gain, final weight, feed intake, and the lowest FCR values followed by C group compared with the other groups. All carcass traits were significantly (p > 0.05) improved by increasing the inclusion levels of Saccharomyces cerevisiae in broiler diets. It could be concluded that the broiler diet supplemented with 2.5 or 3.75 g kg−1 of Saccharomyces cerevisiae as a biodegrading agent resulted in improved growth performance, immunity activity and carcass traits, and supplementation with Saccharomyces cerevisiae at these levels can be used effectively in broiler diets without negatively affecting bird health status.

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Genome Profiling for Aflatoxin B1 Resistance in Saccharomyces cerevisiae Reveals a Role for the CSM2/SHU Complex in Tolerance of Aflatoxin B1-Associated DNA Damage

G3 Genes|Genome|Genetics ◽

10.1534/g3.120.401723 ◽

2020 ◽

Vol 10 (11) ◽

pp. 3929-3947

Author(s):

Nick St. John ◽

Julian Freedland ◽

Henri Baldino ◽

Francis Doyle ◽

Cinzia Cera ◽

...

Keyword(s):

Dna Damage ◽

Dna Adducts ◽

Aflatoxin B1 ◽

Yeast Genome ◽

Actin Reorganization ◽

Functionally Diverse ◽

Next Generation Sequencing Ngs ◽

Pooled Samples ◽

Sister Chromatid Recombination ◽

Human Cyp1a2

Exposure to the mycotoxin aflatoxin B1 (AFB1) strongly correlates with hepatocellular carcinoma (HCC). P450 enzymes convert AFB1 into a highly reactive epoxide that forms unstable 8,9-dihydro-8-(N7-guanyl)-9-hydroxyaflatoxin B1 (AFB1-N7-Gua) DNA adducts, which convert to stable mutagenic AFB1 formamidopyrimidine (FAPY) DNA adducts. In CYP1A2-expressing budding yeast, AFB1 is a weak mutagen but a potent recombinagen. However, few genes have been identified that confer AFB1 resistance. Here, we profiled the yeast genome for AFB1 resistance. We introduced the human CYP1A2 into ∼90% of the diploid deletion library, and pooled samples from CYP1A2-expressing libraries and the original library were exposed to 50 μM AFB1 for 20 hs. By using next generation sequencing (NGS) to count molecular barcodes, we initially identified 86 genes from the CYP1A2-expressing libraries, of which 79 were confirmed to confer AFB1 resistance. While functionally diverse genes, including those that function in proteolysis, actin reorganization, and tRNA modification, were identified, those that function in postreplication DNA repair and encode proteins that bind to DNA damage were over-represented, compared to the yeast genome, at large. DNA metabolism genes also included those functioning in checkpoint recovery and replication fork maintenance, emphasizing the potency of the mycotoxin to trigger replication stress. Among genes involved in postreplication repair, we observed that CSM2, a member of the CSM2(SHU) complex, functioned in AFB1-associated sister chromatid recombination while suppressing AFB1-associated mutations. These studies thus broaden the number of AFB1 resistance genes and have elucidated a mechanism of error-free bypass of AFB1-associated DNA adducts.

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