Characterisation of sin, a potential recombinase-encoding gene from Staphylococcus aureus

Area of Science:

• Molecular Biology
• Genetics
• Microbiology

Background:

• The staphylococcal beta-lactamase (Bla) transposon Tn4002 exhibits specific insertion into a 1.8-kb region of the plasmid pSK1.
• Understanding the genetic basis of this insertional specificity is crucial for studying antibiotic resistance mechanisms.

Purpose of the Study:

• To determine the nucleotide sequences of the specific insertion regions on plasmids pSK1 and pI9789.
• To identify the genetic elements responsible for the high insertional specificity of Tn4002.

Main Methods:

• DNA sequencing of target regions on pSK1 and pI9789.
• Sequence analysis to identify genes and regulatory elements.
• Southern hybridization to determine the distribution of the sin gene across different plasmid families.

Main Results:

• Identification of the sin gene, encoding a protein similar to DNA recombinases, within the target regions.
• Discovery of a dyad symmetry region upstream of sin on both pSK1 and pI9789.
• Southern hybridization confirmed the presence of sin on various Bla and pSK1 family plasmids.
• The dyad symmetry region was identified as the insertion site for Tn552 and Tn4002.

Conclusions:

• The sin gene and the upstream dyad symmetry region are critical for the specific insertion of Tn4002 and Tn552 into Bla plasmids.
• This finding provides insight into the molecular mechanisms of transposon integration in staphylococci.
• The identified elements may play a role in the dissemination of antibiotic resistance genes.