[Complete nucleotide sequence and analysis of Planobispora linear plasmid pPR2]

Area of Science:

• Microbiology
• Molecular Biology
• Genomics

Context:

• Linear plasmids are common in actinomycetes, but their replication mechanisms, especially telomere replication, are not fully understood.
• Planobispora is a genus of actinomycetes that has not previously had a linear plasmid fully sequenced.

Purpose:

• To determine the complete nucleotide sequence of the Planobispora linear plasmid pPR2.
• To identify potential novel proteins and genetic elements involved in its replication, particularly telomere replication and origin of replication.

Summary:

• The complete 15520 bp nucleotide sequence of Planobispora linear plasmid pPR2 was obtained. It lacks typical Streptomyces telomere replication loci and origin replication elements.
• pPR2 encodes a unique protein (pPR2.3c) with domains resembling telomere-associated proteins and helicases, suggesting a novel telomere replication mechanism. It also encodes a single-strand binding protein and a Tra protein.
• The plasmid's terminal inverted repeat cannot form a conserved secondary structure, differing from other Streptomyces linear replicons.

Impact:

• This study reports the first complete nucleotide sequence of a linear plasmid from the genus Planobispora.
• pPR2 is identified as the smallest actinomycete linear plasmid discovered to date outside the Streptomyces genus.
• The findings suggest a novel mechanism for telomere replication in linear plasmids, expanding our understanding of extrachromosomal DNA replication in bacteria.