Selective initiation of replication at origin sequences of the rDNA molecule of physarum polycephalum using synchronous plasmodial extracts

Dianne C. Daniel, Edward M. Johnson

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

A cell-free system using synchronous plasmodial extracts initiates replication selectively on the 60 kb rDNA palindrome of Physarum polycephalum Preferential labeling of rDNA fragments by nuclear extracts, in which elongation is limited, indicates that initiation occurs at two positions corresponding to in vivo origins of replication estimated by electron microscopy. Both nuclear and whole plasmodial extracts initiate selectively within a plasmid, pPHR21, containing one of these origins. In this plasmid bubbles expand bidirectionally and generate Dpnl-resistant DNA. Extracts made at prophase or early S phase, times when the nucleolus is disorganized, are most active in pPHR2l replication. Mapping positions of replication bubbles locates the initiation point in a 3.2 kb BstEII fragment at the upstream border of a series of 31 bp repeats 2.4 kb from the initiation point for ribosomal gene transcription.

Original languageEnglish
Pages (from-to)8343-8362
Number of pages20
JournalNucleic Acids Research
Volume17
Issue number20
DOIs
StatePublished - 25 Oct 1989

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