Stu I problems

Ashok Aiyar aiyar at
Wed Jul 9 12:27:32 EST 1997

On 9 Jul 1997 13:04:34 GMT,
Alan KAY (kay at wrote:
>In article <Pine.A32.3.91.970708110055.75636A-100000 at>, 
>mdamarin at says...
>>Hi there,
>>          I have a problem with a Stu I digestion. I have an insert which 
>>contains a Stu I site that in the 5' end is overllaping with a metilation 
>> forms ccAGGCCT...the ccAGG is the metilaiton site and the 
>>AGGCCT the Stu I site. 

>According to the New England Biolabs catalogue, which is what I usually refer 
>to when I think I may have a methylation problem, Stu I will be blocked by 
>overlapping dcm methylation, but apparently only in the context of AGGCCTGG, 
>so that it is the second C in the recognition site which is methylated. In 
>your sequence context, Stu I should not be inhibited.

The complement of ccAGGCCT is AGGCCTgg, which as you have pointed out,
is a sequence that is not cleaved by StuI, when dcm methylated.

So it is extremely likely that dcm methylation is the reason why the StuI
site in question is recalcitrant to digestion.

Ashok Aiyar, Ph.D.
McArdle Laboratory for Cancer Research
aiyar at

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