Although allostery plays a central role in driving protein–DNA interac-tions, the physical basis of such cooperative behavior remains poorly
understood. In the present study, using isothermal titration calorimetry in
conjunction with site-directed mutagenesis, we provide evidence that an
intricate network of energetically-coupled residues within the basic regions
of the Jun-Fos heterodimeric transcription factor accounts for its allosteric
binding to DNA.
The insect ecdysteroid receptor consists of a heterodimer between EcR and the RXR-orthologue, USP. We addressed the question of whether this heterodimer, like all other RXR heterodimers, may be formed in the absence of ligand and whether ligand promotes dimerization. We found that C-terminal protein fragments that comprised the ligand binding, but not the DNA binding domain of EcR and USP and which were equipped with the activation or DNA binding region of GAL4, respectively, exhibit a weak ability to interact spontaneously with each other.
RNase H2 ofSaccharomyces cerevisiaeconsists of three essential subunits
(Rnh201, Rnh202 and Rnh203) and plays a critical role in the removal of
RNA incorporated in duplex DNA. In the present study, we purified indi-vidual subunits and heterodimeric subcomplexes to examine the assembly
and biochemical function of subunits of RNase H2in vitro.