Partial complementation of a DNA ligase I deficiency by DNA ligase III and its impact on cell survival and telomere stability in mammalian cells

Catherine Le Chalony,Vincent Pennaneach,Julia Gross,Laurent R Gauthier,Denis S Biard,François D Boussin,Françoise Hoffschir

doi:10.1007/s00018-012-0975-8

Abstract

DNA ligase I (LigI) plays a central role in the joining of strand interruptions during replication and repair. In our current study, we provide evidence that DNA ligase III (LigIII) and XRCC1, which form a complex that functions in single-strand break repair, are required for the proliferation of mammalian LigI-depleted cells. We show from our data that in cells with either dysfunctional LigI activity or depleted of this enzyme, both LigIII and XRCC1 are retained on the chromatin and accumulate at replication foci. We also demonstrate that the LigI and LigIII proteins cooperate to inhibit sister chromatid exchanges but that only LigI prevents telomere sister fusions. Taken together, these results suggest that in cells with dysfunctional LigI, LigIII contributes to the ligation of replication intermediates but not to the prevention of telomeric instability.Electronic supplementary materialThe online version of this article (doi:10.1007/s00018-012-0975-8) contains supplementary material, which is available to authorized users.

Highlights

Rapid and appropriate rejoining of single-strand breaks (SSBs) in the DNA duplex is critical to the preservation of genomic integrity [1–7]
We have shown here that in mammalian ligase I (LigI)-deficient cells, ligase III (LigIII) and XRCC1 are retained on chromatin at replication foci and that both proteins are required for the long-term survival of these cells
We further show for the first time that both LigI and LigIII cooperate to suppress sister chromatid exchange (SCE), but that LigIII is not sufficient to prevent sister telomere fusions in LigI-deficient cells, revealing the importance of LigI function in telomere stability

Summary

Introduction

Rapid and appropriate rejoining of single-strand breaks (SSBs) in the DNA duplex is critical to the preservation of genomic integrity [1–7]. The repair of DNA SSBs involves lesion detection, processing, gap filling, and ligation (for reviews see [8–10]). Single-strand break junction defects in patients are associated with the development of neurodegenerative syndromes [11–13] and cancer predisposition [3]. Patients with DNA ligation defects show greater sensitivity to DNA-damaging agents and immunodeficiency [6]. Single-strand discontinuity in the DNA backbone is formed at the replication fork during lagging strand DNA synthesis and is transiently introduced by the action of topoisomerases during replication or transcription to release DNA topological constraints. SSBs are one of the intermediates of several DNA repair pathways that require nucleotide replacement and are formed directly following exposure to ionizing radiation

Methods

Results

Conclusion