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The penicillin gene cluster is amplified in tandem repeats linked by conserved hexanucleotide sequences
F Fierro1, J L Barredo, B Díez
1Section of Microbiology, University of León, Faculty of Biology, Spain.
Summary
Penicillium chrysogenum strains exhibit gene amplification and deletion of penicillin biosynthetic gene clusters. These genetic changes, occurring in tandem repeats linked by conserved sequences, are driven by site-specific recombination.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Penicillin biosynthesis in Penicillium chrysogenum is regulated by specific gene clusters.
- Understanding the genetic mechanisms behind penicillin overproduction is crucial for industrial applications.
Purpose of the Study:
- To investigate the genomic organization and amplification of penicillin biosynthetic genes in Penicillium chrysogenum.
- To elucidate the role of conserved DNA sequences in gene duplication and deletion events.
Main Methods:
- DNA sequencing and analysis of Penicillium chrysogenum strains.
- Comparative genomics to identify gene copy number variations.
- Identification of conserved nucleotide sequences involved in recombination.
Main Results:
- Penicillin biosynthetic genes (pcbAB, pcbC, penDE) are located in a 106.5-kb amplified DNA region in strain AS-P-78.
- Wild-type strains possess a single copy, while overproducer strain E1 shows tandem amplification of a 57.9-kb fragment.
- Deletion mutant npe10 exhibits a precise deletion of the amplified fragment, with recombination occurring at conserved hexanucleotide sequences (TTTACA/TGTAAA).
Conclusions:
- Tandem reiteration and deletion of penicillin gene clusters in Penicillium chrysogenum are mediated by mutation-induced site-specific recombination.
- Conserved hexanucleotide sequences act as key sites for these genetic rearrangements.
- These findings provide insights into the genomic plasticity underlying antibiotic production in fungi.