Transcription is initiated at the beginning of the 162 nucleotide mRNA leader encoded by a DNA region called trpL

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#Unit 3. Fundamental Processes

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

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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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#Unit 3. Fundamental Processes

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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DnaA promotes replication

SeqA delays new round of replication by inhibiting dam methylase binding

Dam methylase provide substrate for DnaA

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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

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#Unit 3. Fundamental Processes

There are two basic types of DNA synthesis