Previous Article | Next Article ![]()
Mol. Cell. Biol., Jul 1997, 3649-3662, Vol 17, No. 7
J Yie, S Liang, M Merika and D Thanos
The mammalian high-mobility-group protein I(Y) [HMG I(Y)], while not a
typical transcriptional activator, is required for the expression of many
eukaryotic genes. HMG I(Y) appears to recruit and stabilize complexes of
transcriptional activators through protein-DNA and protein- protein
interactions. The protein binds to the minor groove of DNA via three short
basic repeats, preferring tracts of adenines and thymines arranged on the
same face of the DNA helix. However, the mode by which these three basic
repeats function together to recognize HMG I(Y) binding sites has remained
unclear. Here, using deletion mutants of HMG I(Y), DNase I footprinting,
methylation interference, and in vivo transcriptional assays, we have
characterized the binding of HMG I(Y) to the model beta-interferon
enhancer. We show that two molecules of HMG I(Y) bind to the enhancer in a
highly cooperative fashion, each molecule using a distinct pair of basic
repeats to recognize the tandem AT-rich regions of the binding sites. We
have also characterized the function of each basic repeat, showing that
only the central repeat accounts for specific DNA binding and that the
presence of a second repeat bound to an adjacent AT-rich region results in
intramolecular cooperativity in binding. Surprisingly, the
carboxyl-terminal acidic tail of HMG I(Y) is also important for specific
binding in the context of the full-length protein. Our results present a
detailed examination of HMG I(Y) binding in an important biological
context, which can be extended not only to HMG I(Y) binding in other
systems but also to the binding mode of many other proteins containing
homologous basic repeats, which have been conserved from bacteria to
humans.
Copyright © 1997, American Society for Microbiology
Intra- and intermolecular cooperative binding of high-mobility-group protein I(Y) to the beta-interferon promoter
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»