Which strand of a plasmid is replicated?

tfitzwater at gilead.com tfitzwater at gilead.com
Thu Sep 14 13:35:59 EST 2000

>From: tfitzwater at gilead.com
>Date: Wed 13 Sep 2000 - 20:40:38 BST

>Leading strand synthesis of ColE 1-type plasmids is directed by the Primer
>RNA, which begins with the sequence 5' GCAAACAAAAAAACC... and ends 555
>nucleotides later with the sequence ...GGGGGGCGGACCUAUGGAAA 3'. DNA
>replication starts from RNase H cuts made at the final 3 A residues and
>continues around the plasmid. Lagging strand replication starts at about
>position 720 downstream from the start of Primer RNA transcription and is
>halted at about position 525 on the non-template strand until the
>replication fork passes that position. Lagging strand synthesis then
>continues until two concatenated double-stranded plasmids result. These
>are then resolved into separate entities.

I was asked for references.  Here are 3:

Nakasu, S. and Tomizawa, J.,1992. Structure of the ColE1 DNA molecule
before segregation to daughter molecules.  Proc. Natl. Acad. Sci. USA

Fitzwater, T., Yang, Y. L., Zhang, X. Y. and Polisky, B., 1992.  Mutations
affecting RNA-DNA hybrid formation of the ColE1 replication primer RNA.
Restoration of RNA I sensitivity to a copy-number mutant by second-site
mutations.  J. Mol. Biol. 226:  997-1008.

Eguchi, Y., Itoh, T. and Tomizawa, J., 1991.  Antisense RNA.  Annu. Rev.
Biochem. 60:631-652.

Tim Fitzwater
Principal Research Associate
Gilead Sciences


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