Nonhomologous end-joining (NHEJ) is a major DNA double-strand break (DSB) repair pathway. NHEJ is initiated through DSB recognition by the DNA end-binding heterodimer, Ku, while end-joining is accomplished by the XRCC4-DNA ligase IV (X4L4) complex. This thesis reports that APLF (Aprataxin and Polynucleotide kinase-Like Factor), an endo/exonuclease with a forkhead-associated (FHA) domain and two unique zinc fingers (ZF), interacts with both Ku and X4L4. The APLF-X4L4 interaction is FHA- and phospho-dependent, and is mediated by CK2 phosphorylation of XRCC4 in vitro. APLF binds Ku independently of the FHA and ZF domains, and complexes with Ku at DNA ends. APLF undergoes ionizing radiation induced ATM-dependent hyperphosphorylation and ATM phosphorylates APLF in vitro. Downregulation of APLF is associated with defective NHEJ and impaired DSB repair kinetics. These results suggest that APLF is an ATM target that is involved in NHEJ and facilitates DSB repair, likely via interactions with Ku and X4L4.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/10435 |
| Date | 25 July 2008 |
| Creators | Macrae, Chloe Jean |
| Contributors | Koch, Christine Anne |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
| Format | 2235434 bytes, application/pdf |
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