After pre-RC assembly and Cdc45 association with the origin of replication, Replication Protein A (RPA) also associates with chromatin. RPA is a heterotrimeric complex containing p70, p34, and p11 subunits, and also is required for DNA recombination and DNA repair. The p70 subunit of RPA binds to the primase subunits of Pol alpha:primase. The p70 and p34 subunits of RPA are phosphorylated in a cell cycle-dependent manner. RPA is a single-strand DNA (ssDNA) binding protein and its association with chromatin at this stage suggests that DNA is partially unwound. This suggestion has been confirmed by detection of ssDNA in budding yeast origins of replication using chemical methods.