080818.PMCB.lecture.6

080818.PMCB.lecture.6 - 8/18/2008 1 lant Molecular and...

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Unformatted text preview: 8/18/2008 1 lant Molecular and Cellular Biology Lecture 6: Regulation & Initiation of DNA Replication Gary Peter 8/18/2008 PMCB Lecture 8: G. Peter 2 Learning Objectives 1. List and explain the structure and function of origins of replication in prokaryotes and eukaryotes 2. Explain the molecular mechanisms that regulate DNA replication of the E. coli genome 3. Explain the molecular mechanisms that regulate plasmid DNA replication 4. Explain the molecular mechanisms that regulate nuclear genome DNA replication in eukaryotes 5. Explain the molecular mechanisms by which telomeres are replicated 8/18/2008 PMCB Lecture 8: G. Peter 3 Origins of DNA Replication z Specific DNA sequences that are the start site for DNA replication z What steps must occur at the origin to initiate DNA replication? 1. Recognition of the sequence 2. Melting of the DNA 3. Assembly of the replisome complex 4. Initiation of leading strand synthesis 8/18/2008 PMCB Lecture 8: G. Peter 4 Plasmids z Extrachromsomal DNA/genomes, usually circular, with survival and propagation functions, including z Replication control z Partitioning z Multimer resolution z Post segregation killing z Conjugative transfer Molecular Microbiology (2000) 37(3), 485-491 8/18/2008 PMCB Lecture 8: G. Peter 5 Control of Plasmid Replication z Replication is central to the control of a number of important plasmid properties: HOST RANGE; COPY NUMBER; INCOMPATIBILITY; and MOBILITY z Some plasmids are able to replicate in a limited number of bacterial species; they have a NARROW host range. Examples are ColE1, pBR322, pUC18 plasmids which are limited to E. coli and some closely related species. z Other plasmids are able to replicate in a wide range of bacterial species; they have a BROAD host range. z The number of copies of a plasmid can vary from 1 (the F plasmid) to over a hundred (pUC18). This number is a property of the plasmid itself and depends on the mechanism by which it regulates its own replication. 8/18/2008 PMCB Lecture 8: G. Peter 6 Plasmid Copy # Control Systems z Negative control systems inhibit the initiation of DNA synthesis z Three general classes each of which depends on the kind of negative control system employed 1. Directly repeated sequences (iterons) that complex with replication inhibitor proteins (Rep) 2. Antisense RNAs that hybrize to complementary regions of...
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080818.PMCB.lecture.6 - 8/18/2008 1 lant Molecular and...

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