Linked Life Data

8289240

Source:http://linkedlifedata.com/resource/pubmed/id/8289240

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1994-2-24
pubmed:abstractText
The effect of base composition in the central region of polypurine.polypyrimidine (Pur.Pyr) tracts on the formation of intramolecular DNA triplexes in plasmids was examined using chemical probes (diethyl pyrocarbonate and OsO4), and two-dimensional (2-D) agarose gel electrophoresis. Two isomers exist for an intramolecular triplex: one with the 3'-half of the Pyr strand as the third strand (H-y3) and the other with the 5'-half of the Pyr strand as the third strand (H-y5). It was shown that the content and position of G + C residues in the triplex loop region (the center of Pur.Pyr tracts) are primary determinants for the isomerization between the H-y3 and H-y5 triplexes. Divalent metal ions such as Mg2+ and negative supercoiling also modulate the isomerization: the H-y5 conformation is stabilized by the divalent metal ions and/or under relatively lower negative supercoiling. 2-D gel analyses revealed that two isomers, H-y3 and H-y5, are topologically non-equivalent: the H-y3 formation relaxes one more supercoil turn than H-y5. As the G + C content in the center of Pur.Pyr tracts increases, the triplex requires more supercoil energy for formation. Therefore, the base-pair opening in the center of Pur.Pyr tracts is the initial and critical step in the pathway for the formation of triplex as well as the isomerization. The role of the triplex loop sequence is explained by a model in which the nucleation process of H-y3 formation requires a wide range of base-pair opening compared to that of H-y5: such unwinding would not be favored for the central region of the duplex with high G + C content and so it would be in the presence of Mg2+, and thereby the H-y5 formation is promoted.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0022-2836
pubmed:author
pubmed:issnType
Print
pubmed:day
7
pubmed:volume
235
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
185-97
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1994
pubmed:articleTitle
The loop sequence plays crucial roles for isomerization of intramolecular DNA triplexes in supercoiled plasmids.
pubmed:affiliation
Laboratory of Analytical Chemistry, Tokyo College of Pharmacy, Japan.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, Non-U.S. Gov't