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A protein that binds to the P1 origin core and the oriC 13mer region in a methylation‐specific fashion is the product of the host seqA gene.
Author(s) -
Brendler T.,
Abeles A.,
Austin S.
Publication year - 1995
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1995.tb00080.x
Subject(s) - methylation , biology , seqa protein domain , dna methylation , gene , genetics , dna , plasmid , origin of replication , microbiology and biotechnology , gene expression
The P1 plasmid replication origin P1oriR is controlled by methylation of four GATC adenine methylation sites within heptamer repeats. A comparable (13mer) region is present in the host origin, oriC. The two origins show comparable responses to methylation; negative control by recognition of hemimethylated DNA (sequestration) and a positive requirement for methylation for efficient function. We have isolated a host protein that recognizes the P1 origin region only when it is isolated from a strain proficient for adenine methylation. The substantially purified 22 kDa protein also binds to the 13mer region of oriC in a methylation‐specific fashion. It proved to be the product of the seqA gene that acts in the negative control of oriC by sequestration. We conclude that the role of the SeqA protein in sequestration is to recognize the methylation state of P1oriR and oriC by direct DNA binding. Using synthetic substrates we show that SeqA binds exclusively to the hemimethylated forms of these origins forms that are the immediate products of replication in a methylation‐proficient strain. We also show that the protein can recognize sequences with multiple GATC sites, irrespective of the surrounding sequence. The basis for origin specificity is primarily the persistence of hemimethylated forms that are over‐represented in the natural. DNA preparations relative to controls.