Although the circular, bidirectionally replicating genome of E. coli has served as a good paradigm for many prokaryotic genomes, it is not the only way that genomes are organized and replicated. With the sequencing of the Lyme's Disease bacterium Borrelia burgdorferi, and the astounding number of linear DNA molecules in this organism, it became evident that, like eukaryotes, prokaryotic organisms needed ways to handle the replication of linear DNA ends. As the NAR paper below states in the Abstract:

"All cells with linear chromosomes must utilize special mechanisms to replicate the extreme termini of their DNA molecules, since DNA polymerases alone are unable to perform this function (1). Most eukaryotes have open-ended DNAs and employ special ‘telomerase’ enzymes for this purpose, but there are other solutions that ensure complete replication of linear DNA: protein priming, recombination and covalently closed terminal hairpins. Phage N15 belongs to the small group of systems known to replicate as linear DNA with hairpin ends. Such replicons are generally of eukaryotic origin, but a few from bacteria are known: for example the phage-plasmids KO2 in Klebsiella oxytoca (2, S.R.Casjens and E.B.Gilcrease, unpublished observations) and PY54 in Yersinia enterocolytica (3), as well as the linear plasmids and chromosomes of Borrelia (4–6) and one of the two chromosomes of Agrobacterium tumefaciens (7,8). "

In this Journal Club we will have a brief overview of linear chromosome end replication and then discuss the paper by Huang et al that presents data for a Topoisomerase IB-like mechanism for chromosome end replication and resolution in prokaryotes.

A couple of other papers:

http://jb.asm.org/cgi/content/abstract/186/13/4134

http://nar.oupjournals.org/cgi/content/full/31/22/6552

The PubMed link to "Protelomerase"

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=pubmed&term=protelomerase

Huang et al paper to be discussed.

Eric S. Miller, Ph.D.
Department of Microbiology
North Carolina State University
Raleigh, NC 27695-7615

919-515-7922
eric_miller@ncsu.edu
www.mbio.ncsu.edu/esm/esm.html