BAC methylation

[Charles S. Gasser]

<x-flowed>ClaI is subject to methylation at overlapping DAM methylation sites
in DAM+ hosts.  Methylation at these sites blocks digestion by ClaI.
The recognition sequence for ClaI is ATCGAT.  If this sequence is
preced by a G or followed by a C then a DAM methylation site (GATC)
is present and can be methylated in a DAM+ strain.  Since most
strains are DAM+, most BAC DNA will be methylated at these sites.
Sites which are not preceded by a G or followed by a C will still be
digested in DNA deriving from DAM+ strains because they will not be
methylated.  There is a good discussion of the different enzymes that
can be affected by DAM methylation in the appendix of the New England
Biolabs catalog.

Hope this helps,
Chuck Gasser

=======================================
Charles S. Gasser, Ph.D.
Professor
Section of Molecular and Cellular Biology
University of California
1 Shields Ave.
Davis, CA  95616

csgasser at ucdavis.edu
http://www-mcb.ucdavis.edu/faculty-labs/gasser/gasser-lab.html
Tel. 530 752-1013
FAX 530 752-3085


---

</x-flowed>