Kid cleaves specific mRNAs at UUACU sites to rescue the copy number of plasmid R1.
Stability and copy number of extra-chromosomal elements are tightly regulated in prokaryotes and eukaryotes. Toxin Kid and antitoxin Kis are the components of the parD stability system of prokaryotic plasmid R1 and they can also function in eukaryotes. In bacteria, Kid was thought to become active only in cells that lose plasmid R1 and to cleave exclusively host mRNAs at UA(A/C/U) trinucleotide sites to eliminate plasmid-free cells. Instead, we demonstrate here that Kid becomes active in plasmid-containing cells when plasmid copy number decreases, cleaving not only host- but also a specific plasmid-encoded mRNA at the longer and more specific target sequence UUACU. This specific cleavage by Kid inhibits bacterial growth and, at the same time, helps to restore the plasmid copy number. Kid targets a plasmid RNA that encodes a repressor of the synthesis of an R1 replication protein, resulting in increased plasmid DNA replication. This mechanism resembles that employed by some human herpesviruses to regulate viral amplification during infection.
Pimentel
Belén
B
MRC, Cancer Cell Unit, Hutchison/MRC Research Centre, Hills Road, Cambridge, UK.
Madine
Mark A
MA
de la Cueva-Méndez
Guillermo
G
D001483:Base Sequence / Q000235:genetics; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000378:metabolism*; D016296:Mutagenesis; D016133:Polymerase Chain Reaction; D011815:R Factors / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*
D017931:DNA Primers; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C489749:ParD protein, Plasmid R1; D012333:RNA, Messenger; C473072:kid toxin protein, E coli plasmid R1