Interactions and CCAAT-Binding of <em>Arabidopsis thaliana</em> NF-Y Subunits

<div><h3>Background</h3><p>NF-Y is a transcription factor that recognizes with high specificity and affinity the widespread CCAAT box promoter element. It is formed by three subunits: NF-YA and the NF-YB/NF-YC- heterodimer containing histone fold domains (HFDs). We previously identified a large <em>NF-Y</em> gene family in <em>Arabidopsis thaliana</em>, composed of 29 members, and characterized their expression patterns in various plant tissues.</p> <h3>Methods</h3><p>We used yeast Two-hybrids assays (Y2H), pull-down and Electrophoretic Mobility Shift Assay (EMSA) <em>in vitro</em> experiments with recombinant proteins to dissect AtNF-YB/AtNF-YC interactions and DNA-binding with different AtNF-YAs.</p> <h3>Results</h3><p>Consistent with robust conservation within HFDs, we show that heterodimerization is possible among all histone-like subunits, including the divergent and related LEC1/AtNF-YB9 and L1L/AtNF-YB6 required for <em>embryo</em> development. DNA-binding to a consensus CCAAT box was investigated with specific AtNF-YB/AtNF-YC combinations and observed with some, but not all AtNF-YA subunits.</p> <h3>Conclusions</h3><p>Our results highlight (i) the conserved heterodimerization capacity of AtNF-Y histone-like subunits, and (ii) the different affinities of AtNF-YAs for the CCAAT sequence. Because of the general expansion of NF-Y genes in plants, these results most likely apply to other species.</p> </div>