Methylation-dependent transcription controls plasmid replication of the CloDF13 cop-1(Ts) mutant

Putten, Arnold J. van; Lang, Ronald de; Veltkamp, E.; Nijkamp, H. J. J.; Solingen, P. van; Berg, Johan

doi:10.1128/jb.168.2.728-733.1986

Cited by 10 publications

(9 citation statements)

References 31 publications

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“…1B). No reproducible hemimethylation was detected at the two MboII sites in pBRpm which do not lie in inverted repeats (positions 468 and 2960), in agreement with previous findings (38 (2,7,41) and mutations in these inverted repeats reduce the effect of methylation on plasmid transformation (36a). These same sites are preferentially undermethylated in mutH+ strains.…”

Section: Resultssupporting

confidence: 79%

The mutH gene regulates the replication and methylation of the pMB1 origin

Russell

Horiuchi

1991

J Bacteriol

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DNA methylation is known to regulate several prokaryotic replication origins. In particular, the Escherichia coli chromosomal origin oriC and the pMB1 plasmid origin (which is homologous to the ColEl origin) replicate poorly when hemimethylated at dam (GATC) sites. Because the mismatch repair protein MutH is known to recognize hemimethylated dam sites, its role in the replication of these origins was investigated. The results presented here show that the mutH gene product is partially responsible for the poor replication of the pMBl origin when hemimethylated but has no effect on the replication of oriC. Methylation levels at individual dam sites suggest that the MutH protein binds to an inverted repeat in the pMBl replication primer promoter. These findings suggest a mechanism for the coordinated control of DNA repair and replication.Both DNA replication and repair require the differentiation of newly replicated molecules from unreplicated molecules. In Escherichia coli, this distinction is made by recognizing hemimethylated dam sites (5'-GATC-3' sequences) produced during semiconservative DNA replication of fully methylated parent molecules. This mechanism was first suggested by Wagner and Meselson (42), who proposed that the absence of methylated adenine residues in newly synthesized DNA strands enabled their identification and preferential correction during mismatch repair. This hypothesis was subsequently verified both in vivo (34) and in vitro (24). The repair system requires the mutH, mutL, mutS, and uvrD gene products, exonuclease I, DNA polymerase III, singlestranded DNA-binding protein (21,24), and the presence of dam sites (20,22). The Dam methylase of E. coli methylates the N6 position of adenines in both strands at dam sites (11,13,19). The MutH protein recognizes and shows weak endonucleolytic activity towards hemimethylated and unmethylated dam sites (43).Newly replicated molecules must also be distinguished during DNA replication, in order to prevent immediate reinitiation and origin amplification. In E. coli, the inhibition of replication produced by hemimethylation prevents reinitiation of newly replicated, hemimethylated daughter molecules. Both oriC and the pMB1 plasmid origin (which is similar to the ColEl origin) replicate effectively when fully methylated or unmethylated but not when hemimethylated (38). In addition, replication of the plasmid prophage of bacteriophage P1 is controlled by methylation (1). The exact molecular mechanisms of these regulations remain unknown at present. However, the fact that recognition of hemimethylated DNA plays a role in both mismatch repair and replication suggests that common processes may be involved.In this report we show that the MutH protein, known to recognize hemimethylated and unmethylated dam sites dur-* Corresponding author. t Present address:

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Section: Resultssupporting

confidence: 79%

The mutH gene regulates the replication and methylation of the pMB1 origin

Russell

Horiuchi

1991

J Bacteriol

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“…We also note that the RNA II UP element contains two recognition sites for the Dam methylase (GATC). It has been proposed previously that DNA methylation plays a role in controlling the RNA II promoter, although it is not known whether the GATC sites in the UP element, in addition to a third GATC site in the Ϫ35 region, contribute to regulation (60). The rrnD P1 UP element also contains a GATC sequence.…”

Section: Discussionmentioning

confidence: 99%

Escherichia coli Promoters with UP Elements of Different Strengths: Modular Structure of Bacterial Promoters

et al. 1998

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The α subunit of Escherichia coli RNA polymerase (RNAP) participates in promoter recognition through specific interactions with UP element DNA, a region upstream of the recognition hexamers for the ς subunit (the −10 and −35 hexamers). UP elements have been described in only a small number of promoters, including the rRNA promoter rrnB P1, where the sequence has a very large (30- to 70-fold) effect on promoter activity. Here, we analyzed the effects of upstream sequences from several additional E. coli promoters (rrnD P1, rrnB P2, λp R, lac, merT, and RNA II). The relative effects of different upstream sequences were compared in the context of their own core promoters or as hybrids to thelac core promoter. Different upstream sequences had different effects, increasing transcription from 1.5- to ∼90-fold, and several had the properties of UP elements: they increased transcription in vitro in the absence of accessory protein factors, and transcription stimulation required the C-terminal domain of the RNAP α subunit. The effects of the upstream sequences correlated generally with their degree of similarity to an UP element consensus sequence derived previously. Protection of upstream sequences by RNAP in footprinting experiments occurred in all cases and was thus not a reliable indicator of UP element strength. These data support a modular view of bacterial promoters in which activity reflects the composite effects of RNAP interactions with appropriately spaced recognition elements (−10, −35, and UP elements), each of which contributes to activity depending on its similarity to the consensus.

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“…Regulation of replication initiation. The frequency of the replication initiation at the origin depends in part on the frequency of RNA II formation by RNA polymerase (34,35,96,223,244,336); however, the main regulation of initiation is exerted during the synthesis of RNA II by a 108-nucleotide antisense transcript termed RNA I (319). By hybridizing to the primer precursor, RNA I inhibits hybrid formation between RNA II and its DNA template, leading to abortive primers (156,184,320,322).…”

Section: Colel and Related Plasmidsmentioning

confidence: 99%