How to perform a DNA Methyltransferase assay?

Francisco J. Alarcon fjgen at
Tue Feb 4 19:41:02 EST 1997

  I have problems in doing Methyltransferase assay.  This is cytosine (C5)
Mtase and I am trying to use Tritiated SAM to check for the
radioincorporation in a DNA substrate.  The target recognition of this
enzyme is not known and I am trying to find the target site. The protein
has been purified and is a fusion protein.  I precipitate the
radiolabelled DNA onto Whatman#3 filters and then wash the filters with
Phosphates to get rid of the background.  When I count the radioactivity
using the Scintillation counter I find that the background itself is too
high.  If you can give me a reference (describing the buffer conditions,
the procedure etc.) it would be of great help to me.  Thank you.

My e-mail address is sjanard at

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