Temporal control of transposition in Tn5

Area of Science:

• Molecular Biology
• Genetics
• Microbiology

Background:

• IS50R is an insertion sequence element of the transposon Tn5.
• IS50R encodes two proteins: a transposase (P1) and a transposition inhibitor (P2), produced from distinct transcripts (m1 and m2).

Purpose of the Study:

• To investigate the regulatory mechanisms governing the expression of IS50R-encoded transposase and inhibitor proteins.
• To determine the factors responsible for the observed temporal changes in m1 and m2 transcript levels and their impact on Tn5 transposition.

Main Methods:

• Quantification of m1 and m2 transcript levels over time after introducing bacteriophage lambda::IS50R DNA into bacterial cells.
• Measurement of message stability for both m1 and m2 transcripts.
• Analysis of the role of the bacterial dam methylation system in regulating transcription kinetics.

Main Results:

• Initial m1:m2 transcript ratios of approximately 1:2 shifted to 1:80 within 3 hours, correlating with changes in protein levels and transposition activity.
• Differences in m1 and m2 transcript levels are attributed to distinct promoter strengths and influenced by the host cell's dam methylation system.
• The m2 transcript exhibits approximately twice the stability of the m1 transcript.

Conclusions:

• The observed changes in IS50R transcript levels and subsequent protein production are primarily mediated by the bacterial dam methylation system, not by IS50R-encoded products.
• Differential message stability, with m2 being more stable than m1, contributes to the altered ratio of inhibitor to transposase, potentially regulating Tn5 transposition.