Revision as of 12:31, 21 October 2019

pBAD-dCas9-J23119-M+

This composite part is the principal design of the inducible CRISPR-based DNA replication interference system, with the 20 bp sgRNA targeting to the M+(top strand) DnaA box on E.coli genome replication initiation region, OriC. In natural situations, M+ is a low affinity box for DnaA binding. By blocking the binding of DnaA protein to M+ box, moderate arrest and inhibition of genome replication initiation is achieved. For more detailed information, see BBa_K3081058

Design

Based on CRISPR-interference method for transcription inhibition, we develop a novel approach for prokaryotic genome replication interference (CRISPRri). Hence, a 20-bp sgRNA is designed to be complementary to OriC, the genome replication origin (Figure 1). Instead of site-directed mutations one by one, CRISPRri allows for 20-bp scan each time. Although CRISPRri requires a PAM ("NGG") sequence to execute its function, we found a high occurrence frequency of PAM in the region of replication origin and all available sgRNAs can cover 76.2% (221 out of 290) of OriC.Seven different targeting sites for dCas9 is designed to test the effect on cell growth. We characterized M+ box in detail.

Figure1. Designed targeted box of CRISPRri and observation methods. Functional DNA boxes located on the genome replication origin. The diagram includes high-affinity DnaA binding boxes (R1, R2 and R4), IHF binding site and region for DNA unwinding. Low-DnaA-binding-affinity boxes, R3 and M, are not shown here. Among these boxes, utilized in the experiment are R1, R3, M, IHF binding box and a target box located at the unwinding site (MR13). Another target box, which is located at the linker sequence between M and R2, is also designed. Control group is poly-adenine.

Sequence and Features