DNA polymerases B et D from the hyperthermophilic Archaea Pyrococcus abyssi : contribution to the study of structure-function relationship

DNA replication is a functionally conserved mechanism among the three domains of lite. This processus is performed by DNA polymerases with two accessories factors, PCNA and RF-C, sliding clamp and clamp loader, respectively. Our model of study, the Euryarchaeota Pyrococcus abyssi, possesses one DNA polymerase, belonging to the Family B, and one DNA polymerase, belonging to the Family D. Tisually, proteins interact with PCNA at a hydrophobic pocket which s formed by the IDCL and the C-terminus, These interactions are mediated through common motifs like the PIP box. We have demonstrated that Pol B has just one PIP box motif at the C terminus, while Pol D has two PIP-type motifs, at the N- and C terminus. Respectively, that interact with PCNA. Besides, this work has permitted to give prominence to that Pol D precisely interacts at the C terminus of PCNA. Besides, RF-C, via its PIP box motif, can maintain PCNA on DNA and can block the Pol D/PCNA complex. In addition, a glycine-rich motif has been characterised in Pol D. This motif, renamed PYF box, is implicated in thermostability of this enzyme and could participate to the interactions between subunits DP1 and DP2. Finally, preliminary work on fluorescence spectroscopy about the study of nucleo-proteic complexes. The investigation of motifs implied in structure-function relationship, let us to complete our knowledge about mechanisms of replicative systems in Archaea and mor precisely on Pol D, which is still unknown.