Replication Initiation in Bacteria

Abstract

The initiation of chromosomal DNA replication starts at a replication origin, which in bacteria is a discrete locus that contains DNA sequence motifs recognized by an initiator protein whose role is to assemble the replication fork machinery at this site. In bacteria with a single chromosome, DnaA is the initiator and is highly conserved in all bacteria. As an adenine nucleotide binding protein, DnaA bound to ATP is active in the assembly of a DnaA oligomer onto these sites. Other proteins modulate DnaA oligomerization via their interaction with the N-terminal region of DnaA. Following the DnaA-dependent unwinding of an AT-rich region within the replication origin, DnaA then mediates the binding of DnaB, the replicative DNA helicase, in a complex with DnaC to form an intermediate named the prepriming complex. In the formation of this intermediate, the helicase is loaded onto the unwound region within the replication origin. As DnaC bound to DnaB inhibits its activity as a DNA helicase, DnaC must dissociate to activate DnaB. Apparently, the interaction of DnaB with primase (DnaG) and primer formation leads to the release of DnaC from DnaB, which is coordinated with or followed by translocation of DnaB to the junction of the replication fork. There, DnaB is able to coordinate its activity as a DNA helicase with the cellular replicase, DNA polymerase III holoenzyme, which uses the primers made by primase for leading strand DNA synthesis.

PprA interacts with replication proteins and affects their physicochemical properties required for replication initiation inDeinococcus radiodurans

“…352Earlier, it has been shown that ATP hydrolysis by DnaA is required for melting of AT rich 353 region in oriC followed by initiation of replication(Messer, 2002; Chodavarapu & Kaguni, 354 16 2016). The oligomerisation of both DnaA and DnaB is required for their sequential loading at 355 oriC, unwinding of DNA duplex and generation of replication fork, respectively(Arai and 356 Kornberg, 1981;Chodavarapu & Kaguni, 2016;Patel and Picha, 2000). Here, we report that 357…”

“…It has been shown in E. coli that DnaA-ATP oligomer binds to DnaA 50 boxes at oriC and unwinds the adjacent AT rich region. Subsequently, a hexameric complex 51 of replicative helicase DnaB and its loader DnaC (DnaB 6 -DnaC 6 ) is recruited to the unwound 52 region in oriC resulting to the formation of pre-priming complex (Skarstad and Katayama,53 2013; Chodavarapu and Kaguni, 2016). This provides the site for binding of primase and 54 activation of various events required for the progression of replication complex comprised of 55 DNA polymerase III holoenzyme.…”

“…Involvement of genome segregation proteins like Soj and Spo0J in case of Bacillus 342 subtilis (Ogura et al, 2003; Murray and Errington, 2008; Scholefield et al, 2011) and ParA 343 and ParB in the regulation of secondary genome copy number in D. radiodurans (Maurya et 344 al., 2019a, 2019b) have also been suggested. In case of oriC mediated initiation of DNA 345 replication, DnaA binding at oriC site triggers the recruitment of (DnaB)6-(DnaC)6 346hexameric replicative helicase in several bacteria(Chodavarapu and Kaguni, 2016). Once the 347 helicase is bound to oriC, the dissociation of DnaC from DnaB is required for subsequent 348 round of DNA replication.…”

Identification of the Unwinding Region in the Clostridioides difficile Chromosomal Origin of Replication

“…In all bacteria, DNA replication is a tightly regulated process that occurs with high fidelity and efficiency, and is essential for cell survival. The process involves many different proteins that are required for the replication process itself, or to regulate and aid replisome assembly and activity ( Katayama et al, 2010 ; Murray and Koh, 2014 ; Chodavarapu and Kaguni, 2016 ; Jameson and Wilkinson, 2017 ; Schenk et al, 2017 ). Replication initiation and its regulation arguably are candidates for the search for novel therapeutic targets ( Fossum et al, 2008 ; Grimwade and Leonard, 2017 ; van Eijk et al, 2017 ).…”

Insufficient levels of the nrdAB‐encoded ribonucleotide reductase underlie the severe growth defect of the Δhda E. coli strain

“…DNA replication in E. coli initiates at a single origin, oriC , by a mechanism that requires the DnaA protein (Crooke et al ., ; Margulies and Kaguni, ; Kaguni, ; Duderstadt et al ., ; Leonard and Grimwade, ; Chodavarapu and Kaguni, ). The ATP‐bound form of the DnaA replication initiator protein (DnaA‐ATP) is active for initiation of replication.…”