Protein Lysine Acetylation Regulates the Choice of the Okazaki Fragment Maturation Pathway

Abstract

Eukaryotic DNA replication machinery has evolved to accurately maintain the human genome through decades of life and across generational time. Mutations in the genome can initiate and promote human diseases, such as cancer and neurodegenerative disorders. During replication, lagging strand synthesis initiated by the error‐prone DNA polymerase alpha primes template DNA with a RNA/DNA initiator primer. This is further elongated by high‐fidelity DNA polymerase delta, creating short stretches of DNA, known as Okazaki fragments. Because millions of these fragments need to be created and accurately ligated per cell division, the risk of mutagenesis is higher in the lagging strand compared to the leading strand. Maturation of the Okazaki fragment necessitates the displacement of the initiator primer, to remove the RNA segment prior to ligation. Two redundant pathways have been proposed in this process, one, known as the short flap pathway, rapidly removes the RNA primer and allows ligation of the polymerase alpha synthesized DNA primer. The other pathway, known as the long flap pathway, promotes displacement of the entire initiator primer and the region is resynthesized by the high‐fidelity DNA polymerase delta. Many of the proteins involved in Okazaki fragment maturation pathway are post‐translationally modified by lysine acetylation. Biochemical studies analyzing enzymatic properties of in vitro acetylated Okazaki fragment proteins show alterations in protein‐DNA, protein‐protein interactions and enzyme function. Our preliminary analysis of in vitro acetylated recombinant Okazaki fragment processing (OFP) proteins show that lysine acetylation regulates enzyme activity in a manner consistent with promoting the long flap pathway. Lysine acetylation inhibits the function of the short flap pathway nuclease, flap endonuclease 1 (FEN1) and stimulates the functions of nearly all the proteins in the long flap pathway. Further, using reporter constructs, we showed that in mammalian cells, increasing cellular lysine acetylation correlated with use of the long flap pathway for repair processing. Our current model proposes that lysine acetylation of Okazaki fragment proteins regulates the choice of the long flap pathway, resulting in higher‐fidelity lagging strand synthesis.Support or Funding InformationThis work was supported by funding from National Institute of Health (GM098328) and IUPUI New Faculty Startup Award.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.