Streptomycete origin of chromosomal replication with two putative unwinding elements

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• DNA replication initiation is crucial for bacterial chromosome duplication.
• The origin of replication (oriC) and initiator protein (DnaA) are key players in this process.
• Limited understanding exists for replication initiation in diverse bacterial species like Streptomyces.

Purpose of the Study:

• To elucidate the mechanism of DNA replication initiation in Streptomyces.
• To characterize the structure and function of the Streptomyces oriC region.
• To investigate the role of DnaA binding and DNA unwinding elements (DUEs).

Main Methods:

• In silico analysis using WebSIDD algorithm.
• In vitro P1 nuclease assays.
• In vivo replication initiation point mapping.
• Identification of DnaA-binding motifs.

Main Results:

• Identified 14 DnaA-binding motifs and the consensus DnaA box sequence in Streptomyces.
• Discovered two putative DNA unwinding elements (DUE1 and DUE2) near each other within oriC.
• In vitro assays showed DNA unwinding at both DUE1 and DUE2.
• In vivo mapping confirmed only DUE2 as the functional site for replication initiation.

Conclusions:

• Streptomyces oriC possesses two potential DUEs, but only one is utilized in vivo.
• Transcriptional activity of the oriC region may regulate the choice between DUE1 and DUE2.
• This provides new insights into the regulation of DNA replication initiation in Streptomyces.