Difference between revisions of "Team:HZAU-China/Project/Description"
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Revision as of 08:55, 28 October 2017
Description
In the long history of life evolution, different species living in different environment developed the most adaptive
surviving mechanism for them under the selection pressure, among which some unmatchable become widly preserved in
different creatures, and the mechanism of replication is one of them. The majority of prokaryote share the same mechanism
of self-replication including DNA replication, chromosome seperation and cell division. These three parts comprised
the whole cell cycle, and the main model creature for researching the replication process is E.coli, which at the
same time is the main object of our project.
The replication process of E.coli replication can be devided into phase B,C and D, three phases. Phase B, also called
pre-replication phase, is for DNA replication proparation similar as G1 phase in eukaryote cell cycle. Phase C is
regarded as replication phase during which the chromosome is replicating corespond to the S phase in eukaryote. The
last phase, phase D, is called post-replication phase, in which the behave of chromosome seperation and cell division
happend just like what happened in G2 and M phase of eukaryote cells. the time of C phase and D phase in a generation
is relative constant, so what actually determines the cell cycle is the initiation of genome replication. We know
that cell have to garantee that each cell should have at least one chormosome, and this requires a highly coordination
between DNA replication and cell divsion. Though the delicate mechanism of the corrdination is still a puzzle, it
is clear that DnaA protein plays a significant role in this event. DnaA is a versatile protein, it can not only behave
like a helicase opening the duble-helix of replication initiation site, OriC, while have the function of raising
other proteins forming into the replisome to prolong the replication, but also can anchor the replicationg choromosome
on the cell membrane leading the following seperation of chromosome. But what makes it the linker between replication
and division is that its concentration determines the initiation volume of replication. So according to these information,
we think that regulating the combination of DNA and DnaA protein will be an efficient method to regulate cell replication.
For more information please click here.
There will be about 1h for an entire genome replication, but cell division can reach about 20min per generation. this
reflects the multi-copy number of bacterial genome and only with this mechanism can E.coli reproduce in such a high
speed. what's worse is that even isogenic cells grow in the same culture have a scattering distribution not only
in phase but also in genome copy number. the strong heterogenic in cell cycle and genome copy number hinds the 3D
genome research and may be a potential noise on genome gene expression. At the same time, the developing synthetic
biology requires an approach that can control cell reproduction and can be easily incorporated into circuits, so
that the whole system can be more safe and controlable. taking these into consider, we decided to use CRISPRi to
inhibit its cell cycle, for more details please see design.
But barely pause the replication in some circumstance can't satisfy our needs, and long time inhibition will prolong its length, so there is a need to totally control its replication, not only block but also open. with that purpose we decided to use optogentic to control this system, and the operablity of light to computer makes our system programable, which can be called 4C.
But barely pause the replication in some circumstance can't satisfy our needs, and long time inhibition will prolong its length, so there is a need to totally control its replication, not only block but also open. with that purpose we decided to use optogentic to control this system, and the operablity of light to computer makes our system programable, which can be called 4C.
