Team:Imperial College London/M3/DamMethylation

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(Dam methylation)
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==Dam methylation==
==Dam methylation==
[[Image:II09_Dam action2.jpg| right]]
[[Image:II09_Dam action2.jpg| right]]
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Restriction enzymes often come together with methylation enzymes to form a restriction-modification system.  This well-known combination prevents the genome of the cell from being cleaved by its own restriction enzyme. <br>
+
Restriction enzymes often come together with methylation enzymes to form a restriction-modification system.  This well-known combination prevents the genome of the cell from being cleaved by its own restriction enzymes. <br>
<br>
<br>
-
Methylation as a protection device against resriction enzymes is well documented, and has been proven to work.  There is a strong asymmetry between the function of restriction enzymes and methylases.  Restriction enzymes can cause just one cleavage, which if unrepaired, kills the cell.  However, to effectively protect the cell, methylases need to methylate all the recognition sites. Endogenous promoters are preferred in this case as the fine balance that exists naturally between rstriction enzymes and methylases can be easily disrupted. <br>
+
There is a strong asymmetry between the function of restriction enzymes and methylases.  Restriction enzymes can cause just one cleavage, which if unrepaired, kills the cell.  However, to effectively protect the cell, methylases need to methylate all the recognition sites. There is a fine balance that exists naturally between rstriction enzymes and methylases which can be easily disrupted. This is why endogenous promoters are often preferred.<br>
<br>
<br>
-
In our system, to protect against DNA destruction due to basal levels of restriction enzyme production, we have made use of the native E. coli Dam methylase protection system.  The Dam system is chosen as both DpnII and TaqI enzyme activity can be blocked by Dam methylation.<br>
+
Methylation as a protection device against resriction enzymes is well documented, and has been proven to work.  In our system, to protect against DNA destruction due to basal levels of restriction enzyme production, we have made use of the native E. coli Dam methylase protection system.  The Dam system is chosen as both DpnII and TaqI enzyme activity can be blocked by Dam methylation.<br>
<br>
<br>
Dam methylases recognise the sequence GATC and methylate the Adenine base.  This prevents the restriction enzymes from recognising the sequence and cleaving it.  Therefore, only high levels of restriction enzyme (ie. after thermal triggering) will cleave the DNA. <br>
Dam methylases recognise the sequence GATC and methylate the Adenine base.  This prevents the restriction enzymes from recognising the sequence and cleaving it.  Therefore, only high levels of restriction enzyme (ie. after thermal triggering) will cleave the DNA. <br>

Revision as of 23:21, 11 October 2009

Contents

II09 Thumb m3.pngModule 3: Genome Deletion Overview

Dam methylation

II09 Dam action2.jpg

Restriction enzymes often come together with methylation enzymes to form a restriction-modification system. This well-known combination prevents the genome of the cell from being cleaved by its own restriction enzymes.

There is a strong asymmetry between the function of restriction enzymes and methylases. Restriction enzymes can cause just one cleavage, which if unrepaired, kills the cell. However, to effectively protect the cell, methylases need to methylate all the recognition sites. There is a fine balance that exists naturally between rstriction enzymes and methylases which can be easily disrupted. This is why endogenous promoters are often preferred.

Methylation as a protection device against resriction enzymes is well documented, and has been proven to work. In our system, to protect against DNA destruction due to basal levels of restriction enzyme production, we have made use of the native E. coli Dam methylase protection system. The Dam system is chosen as both DpnII and TaqI enzyme activity can be blocked by Dam methylation.

Dam methylases recognise the sequence GATC and methylate the Adenine base. This prevents the restriction enzymes from recognising the sequence and cleaving it. Therefore, only high levels of restriction enzyme (ie. after thermal triggering) will cleave the DNA.


References

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