Transcription termination maintains chromosome integrity

Area of Science:

• Molecular Biology
• Genetics
• Microbiology

Background:

• DNA replication fork progression can be hindered by collisions with transcription elongation complexes (TECs).
• Transcription termination is crucial for preventing TECs from obstructing DNA replication, which can lead to replication fork arrest and DNA double-strand breaks.

Purpose of the Study:

• To investigate the role of Rho-dependent transcription termination in preventing DNA double-strand breaks.
• To elucidate the mechanism by which transcription termination factors safeguard DNA replication.

Main Methods:

• Inhibition of Rho-dependent transcription termination using bicyclomycin in Escherichia coli.
• Analysis of double-strand break formation in wild-type and mutant strains (nusA, nusG, rpoB*35, recB, ruvC, rep, priA).
• Assessment of DNA replication dependency and replication fork collapse.

Main Results:

• Bicyclomycin treatment induced DNA double-strand breaks, dependent on DNA replication.
• Mutations in Rho co-factors (nusA, nusG) led to hypersensitivity to bicyclomycin and chromosome fragmentation.
• An RNA polymerase mutation (rpoB*35) conferring TEC destabilization significantly increased resistance to bicyclomycin.

Conclusions:

• Rho-dependent transcription termination is essential for preventing replication fork arrest and DNA double-strand breaks.
• The findings support a model where Rho releases obstructing TECs in response to a translocating replisome, ensuring genome integrity.