IS10 transposition is regulated by DNA adenine methylation

Area of Science:

• Molecular Biology
• Genetics
• Microbiology

Background:

• IS10 transposition is a key genetic process in E. coli.
• DNA adenine methyltransferase (dam) methylation plays a role in regulating genetic elements.
• IS10 contains specific dam methylation sites critical for its activity.

Purpose of the Study:

• To investigate the impact of dam methylation on IS10 transposition activity.
• To determine the mechanism by which dam deficiency leads to increased IS10 activity.
• To explore the potential role of DNA replication in IS10 transposition.

Main Methods:

• Analysis of IS10 transposition rates in dam-deficient (dam-) and wild-type (dam+) E. coli strains.
• Examination of IS10 methylation states, including fully methylated and hemimethylated forms.
• Assessing the activity of the transposase promoter and inner terminus in relation to methylation.

Main Results:

• Dam- mutants exhibit significantly increased IS10 transposition.
• Absence of dam methylation at IS10 sites elevates both promoter and terminus activity, fully explaining increased transposition.
• Hemimethylated IS10 elements show substantially higher transposition activity, with one form being over 1000 times more active than fully methylated IS10.
• IS10 promoter and terminus are coordinately activated in a dam-dependent manner, likely due to simultaneous hemimethylation.

Conclusions:

• Dam methylation is a critical negative regulator of IS10 transposition.
• IS10 transposition is strongly influenced by the methylation status of its DNA elements.
• IS10 transposition may be preferentially linked to the cell cycle, occurring during the hemimethylated state immediately following DNA replication.