Download Dinucleotide patterns and nucleosome positioning

Nucleosomes
 Nucleosomes consist of DNA tightly wrapped around
proteins called histones
 75-90% of DNA is believed to be present in
nucleosomes
From faculty web
page of
Grant Hartzog at
the University of
California, Santa
Cruz.
(http://biomedical.
ucsc.edu/Hartzog.
html)
© 2005 Prentice Hall Inc. / A Pearson Education Company / Upper Saddle River, New Jersey 07458
Dinucleotide patterns and nucleosome
positioning
 Dinucleotide patterns
are known to repeat in
DNA wrapped around
histones
 Researchers built
predictive
thermodynamic model
 Accurately predicted
nucleosome
positioning 54% of
time
 Beats 39% accuracy
predicted by chance
From Figure 1 in Segal E. et al. (2006) “A genomic
code for nucleosome positioning” Nature 442: 772778.
© 2005 Prentice Hall Inc. / A Pearson Education Company / Upper Saddle River, New Jersey 07458
Biological implications
From Figure 4 in Segal E. et al. (2006) “A genomic
code for nucleosome positioning” Nature 442: 772778.
© 2005 Prentice Hall Inc. / A Pearson Education Company / Upper Saddle River, New Jersey 07458
Caveats
 Accuracy of mapping could be improved
 DNA sequences longer than dinucleotides are
likely to contribute to positioning code
 Chromatin remodeling factors likely to perturb
nucleosome code
 Experiments with H1 histone protein suggest
that these proteins may alter the way the
nucleosome code is interpreted
© 2005 Prentice Hall Inc. / A Pearson Education Company / Upper Saddle River, New Jersey 07458