The invention relates to a method of enhancing a DNA polymerase reaction by including in a reaction mixture containing a DNA polymerase a protein of DNA ligase. Also provided herein are vectors and host cells comprising those nucleic acid sequences, chimeric polypeptide molecules comprising the polypeptides of the present invention fused to heterologous polypeptide sequences, antibodies which bind to the polypeptides of the present invention and to methods for producing the polypeptides of the present invention. Initially, image information or one or more intensity signals of the overlay target are provided.