Affiliation:
1. Molecular and Cell Biology Program, University of Maryland, Baltimore, and Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21202
Abstract
ABSTRACT
We report on the identification and first cloning of an autonomously replicating sequence element from the chromosome of an archaeon, the extreme halophile
Halobacterium
strain NRC-1. The putative replication origin was identified by association with the
orc7
gene and replication ability in the host strain, demonstrated by cloning into a nonreplicating plasmid. Deletion analysis showed that sequences located up to 750 bp upstream of the
orc7
gene translational start, plus the
orc7
gene and 50 bp downstream, are sufficient to endow the plasmid with replication ability, as judged by expression of a plasmid-encoded mevinolin resistance selectable marker and plasmid recovery after transformation. Sequences located proximal to the two other chromosomally carried haloarchaeal
orc
genes (
orc6
and
orc8
) are not able to promote efficient autonomous replication. Located within the 750-bp region upstream of
orc7
is a nearly perfect inverted repeat of 31 bp, which flanks an extremely AT-rich (44%) stretch of 189 bp. The replication ability of the plasmid was lost when one copy of the inverted repeat was deleted. Additionally, the inverted repeat structure near
orc7
homologs in the genomic sequences of two other halophiles,
Haloarcula marismortui
and
Haloferax volcanii
, is highly conserved. Our results indicate that, in halophilic archaea, a chromosomal origin of replication is physically linked to
orc7
homologs and that this element is sufficient to promote autonomous replication. We discuss the finding of a functional haloarchaeal origin in relation to the large number of
orc1
-
cdc6
homologs identified in the genomes of all haloarchaea to date.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
76 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献