TY - JOUR
T1 - Novel growth rate control of dam gene expression in Escherichia coli
AU - Rasmussen, L J
AU - Marinus, M G
AU - Løbner-Olesen, A
PY - 1994/5
Y1 - 1994/5
N2 - Transcription of the dam gene in Escherichia coli is growth rate regulated by a mechanism distinct from that used for ribosomal RNA gene promoters. Single-copy operon fusions to lacZ indicated that the major promoter, P2, is responsible for most or all of the growth rate dependence. Promoter P2 is a typical sigma 70 promoter with 18 bp spacing between the -10 and -35 hexamers. Primer extension analysis was used to show that there was no inhibition of transcription from promoter P2 in cells induced for the stringent response. Beta-galactosidase specific activity from a single-copy dam::lacZ fusion was unaffected by either excess rrnB RNA or the level of Fis protein. Thus growth rate control of dam gene expression differs from that of the rRNA and tRNA genes by its lack of response to stringent control, ribosomal feedback and enhanced transcription by Fis protein. We devised a procedure for selection of mutant cells in which dam gene expression was unregulated. One such mutant (cde-4), obtained by miniTn10 insertion, showed the same level of beta-galactosidase activity at all growth rates tested. In contrast, growth rate-dependent expression of the rrnB gene was unaffected by cde-4 confirming the different modes of regulation. The cde-4::miniTn10 insertion is located close to kilobase 670 on the physical map in or near the lipB gene.
AB - Transcription of the dam gene in Escherichia coli is growth rate regulated by a mechanism distinct from that used for ribosomal RNA gene promoters. Single-copy operon fusions to lacZ indicated that the major promoter, P2, is responsible for most or all of the growth rate dependence. Promoter P2 is a typical sigma 70 promoter with 18 bp spacing between the -10 and -35 hexamers. Primer extension analysis was used to show that there was no inhibition of transcription from promoter P2 in cells induced for the stringent response. Beta-galactosidase specific activity from a single-copy dam::lacZ fusion was unaffected by either excess rrnB RNA or the level of Fis protein. Thus growth rate control of dam gene expression differs from that of the rRNA and tRNA genes by its lack of response to stringent control, ribosomal feedback and enhanced transcription by Fis protein. We devised a procedure for selection of mutant cells in which dam gene expression was unregulated. One such mutant (cde-4), obtained by miniTn10 insertion, showed the same level of beta-galactosidase activity at all growth rates tested. In contrast, growth rate-dependent expression of the rrnB gene was unaffected by cde-4 confirming the different modes of regulation. The cde-4::miniTn10 insertion is located close to kilobase 670 on the physical map in or near the lipB gene.
KW - Base Sequence
KW - Carrier Proteins/genetics
KW - Cell Division/genetics
KW - Chromosome Mapping
KW - DNA, Bacterial/genetics
KW - Escherichia coli/enzymology
KW - Escherichia coli Proteins
KW - Factor For Inversion Stimulation Protein
KW - Feedback
KW - Gene Expression Regulation, Bacterial
KW - Genes, Bacterial
KW - Integration Host Factors
KW - Methyltransferases/genetics
KW - Molecular Sequence Data
KW - Mutation
KW - Promoter Regions, Genetic
KW - Ribosomes/metabolism
KW - Site-Specific DNA-Methyltransferase (Adenine-Specific)
KW - Transcription, Genetic
M3 - Journal article
C2 - 7934887
SN - 0950-382X
VL - 12
SP - 631
EP - 638
JO - Molecular Microbiology
JF - Molecular Microbiology
IS - 4
ER -