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Journal of Bacteriology, July 1999, p. 4050-4061, Vol. 181, No. 13
Department of Microbiology, Molecular
Biology, and Biochemistry, University of Idaho, Moscow, Idaho
83844-3052
Received 22 April 1998/Accepted 10 December 1998
Like most temperate bacteriophages, phage Mx8 integrates into a
preferred locus on the genome of its host, Myxococcus
xanthus, by a mechanism of site-specific recombination. The Mx8
int-attP genes required for integration map within a
2.2-kilobase-pair (kb) fragment of the phage genome. When this fragment
is subcloned into a plasmid vector, it facilitates the site-specific
integration of the plasmid into the 3' ends of either of two tandem
tRNAAsp genes, trnD1 and trnD2,
located within the attB locus of the M. xanthus
genome. Although Int-mediated site-specific recombination occurs
between attP and either attB1 (within
trnD1) or attB2 (within trnD2), the
attP × attB1 reaction is highly favored and often is
accompanied by a deletion between attB1 and
attB2. The int gene is the only Mx8 gene
required in trans for attP × attB
recombination. The int promoter lies within the 106-bp
region immediately upstream of one of two alternate GTG start codons,
GTG-5208 (GTG at bp 5208) and GTG-5085, for integrase and likely is
repressed in the prophage state. All but the C-terminal 30 amino acid
residues of the Int protein are required for its ability to mediate
attP × attB recombination efficiently. The
attP core lies within the int coding sequence,
and the product of integration is a prophage in which the 3' end of
int is replaced by host sequences. The prophage
intX gene is predicted to encode an integrase with a different C terminus.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Site-Specific Recombination of Temperate
Myxococcus xanthus Phage Mx8: Genetic Elements Required
for Integration
*
Corresponding author. Mailing address: Department of
Microbiology, Molecular Biology, and Biochemistry, University of Idaho, Moscow, ID 83844-3052. Phone: (208) 885-0571. Fax: (208) 885-6518. E-mail: pay{at}uidaho.edu.
This work is dedicated to the memory of Hatch Echols, teacher and friend.
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