A POTENTIAL REGULATORY ROLE OF THE N-TERMINAL DOMAIN OF DNA2 DURING OKAZAKI FRAGMENT MATURATION

초록

The Saccharomyces cerevisiae Dna2 protein involved in Okazaki fragment processing is a multifunctional enzyme. Deletion of its N-terminal 405 amino acids did not cause any loss of the two-enzymatic activities of Dna2; helicase and single-stranded DNA-specific endonuclease. However, cells with a mutant DNA2 allele (dna2D405N) lacking the N-terminal 405 amino acids were severely impaired in growth, being unable to grow at 37 °C, indicating that the N-terminal region contains a domain critical for a cellular function(s) of Dna2. In order to understand the biological role of the N-terminal domain, we examined and compared the enzymological properties of Dna2D405N mutant enzyme with those of wild type one. The two proteins displayed differences in efficiency of substrate utilization. In addition, the N-terminal region was specifically phosphorylated by Cdc7/Dbf4 kinase complex and Rad53, a kinase that is activated upon DNA damage. Consistent with this, either Cdc7 or Dbf4 rescued the temperature growth defect caused by the N-terminal deletion. This suggests a potential linking between DNA replication and cell cycle regulation. We are currently investigating the influence of phosphorylation on the enzyme activities of Dna2 and its relevance to cell cycle control.