Luca Pellegrini's group have published a paper in PNAS entitled "Structures of human primase reveal design of nucleotide elongation site and mode of Pol alpha tethering". DNA synthesis during duplication of the genome depends on primase, the DNA-dependent RNA polymerase that initiates nucleotide polymerization by assembling short RNA primers on the unwound template DNA. The mechanism of DNA priming has remained poorly understood, mainly because of lack of high-resolution structural information. The study has now provided crystal structures of human primase in unliganded form and bound to UTP. The atomic model of primase has been used to map amino acids that are important for the catalytic function of the enzyme. The structure of the complex shows the interaction between primase and DNA polymerase alpha, which keeps primase tethered to the replication fork.