A physical and functional interaction between yeast Pol4 and Dnl4-Lif1 links DNA synthesis and ligation in nonhomologous end joining.
Genetic studies have implicated the Saccharomyces cerevisiae POL4 gene product in the repair of DNA double-strand breaks by nonhomologous end joining. Here we show that Pol4 preferentially catalyzes DNA synthesis on small gaps formed by the alignment of linear duplex DNA molecules with complementary ends, a DNA substrate specificity that is compatible with its predicted role in the repair of DNA double-strand breaks. Pol4 also interacts directly with the Dnl4 subunit of the Dnl4-Lif1 complex via its N-terminal BRCT domain. This interaction stimulates the DNA synthesis activity of Pol4 and, to a lesser extent, the DNA joining activity of Dnl4-Lif1. Notably, the joining of DNA substrates that require the combined action of Pol4 and Dnl4-Lif1 is much more efficient than the joining of similar DNA substrates that require only ligation. Thus, the physical and functional interactions between Pol4 and Dnl4-Lif1 provide a molecular mechanism for both the recruitment of Pol4 to in vivo DNA double-strand breaks and the coupling of the gap filling DNA synthesis and DNA joining reactions that complete the microhomology-mediated pathway of nonhomologous end joining.
Tseng
Hui-Min
HM
Department of Molecular Medicine and Institute of Biotechnology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78245-3207, USA.
Tomkinson
Alan E
AE
D004247:DNA / Q000096:biosynthesis*; D019951:DNA Polymerase beta / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair; D004261:DNA Replication; D004271:DNA, Fungal; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005800:Genes, Fungal; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; C114091:LIF1 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D004247:DNA; D019951:DNA Polymerase beta