DnaA mutants make replication asynchronous

SeqA mutant cells don’t delay rereplication for 13 minutes

Dam methylase mutants stops rereplication

SeqA-/dam+ accumulation of methylated products

SeqA+/dam- accumulation of hemimethylated products

SeqA-/dam- accumulation of hemimethylated products

TLS Online TPP Program

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SeqA is part of a negative regulatory circuit that prevents origins from being remethylated.

TLS Online TPP Program

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#Unit 3. Fundamental Processes

Mutations in dnaA render replication asynchronous, which suggests that DnaA could be the “titrator” or “clock” that measures the number of origins relative to cell mass.

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dat locus is regulatory

In particular, a locus called dat has a large concentration of DnaA-binding sites. It binds about 80 more DnaA molecules than the origin.

Deletion of dat causes initiation to occur more frequently. This significantly increases the amount of DnaA available to the origin.

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#Unit 3. Fundamental Processes

DnaA promotes replication

SeqA delays new round of replication by inhibiting dam methylase binding

Dam methylase provide substrate for DnaA

TLS Online TPP Program

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#Unit 3. Fundamental Processes

There are two basic types of DNA synthesis

TLS Online TPP Program

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#Unit 3. Fundamental Processes

Semiconservative replication

DNA repair reaction