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2004
LSU-HHMI Summer Undergraduate Research Program |
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 Kevin
Bauerle, Anne Grove, Biological Sciences
Domain-Domain Interactions in the Saccharomyces cerevisiae
HMGB Protein HMO1
High Mobility Group proteins (HMGB) are the most abundant non-histone
proteins in the cell nucleus. Their ability to bind, bend, supercoil,
and loop DNA with little or no sequence preference enables these
architectural proteins to play a vital role in recombination,
replication, transcription, and repair. These proteins can also
recognize DNA in a structure specific manner. HMO1 is comprised
of two domains, BoxA and BoxB, and a lysine-rich carboxy-terminus.
This protein contains a single HMG box, Box B, and is one of
seven Saccharomyces cerevisiae HMGB proteins. It is required
for normal growth, plasmid stability, and for the integrity
of the yeast chromatin. Studies have also suggested that HMO1
may act as an RNA polymerase I factor, aid in mutagenesis control,
interact with yeast cellular protein FKBP12, and stimulate enhanceosome
assembly by an Epstein-Barr viral activator. Here, we describe
the preliminary findings of a study designed to determine the
DNA-binding capabilities of BoxA, BoxB, and the basic tail region
and the mechanism by which these regions interact. Thus far,
we have concluded that BoxA does weakly interact with DNA. Furthermore,
circular dichroism spectroscopy has revealed that HMO1 undergoes
thermal denaturation in a manner consistent with that of a two
domain protein by unfolding in two transitions at 23OC and 57OC,
while BoxA unfolds in one transition at 52OC. The discrepancy
in the melting temperatures between one of the two melting temperatures
of HMO1 and the melting temperature of BOXA can be attributed
to interactions between the three regions of HMO1.
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