| dc.description.abstract | The DNA damage response is a complex signalling network that guards cellular genomic integrity and protects organisms from a number of diseases including cancer. Quantitative proteomics revealed that the microtubule-associated proteins, MAP7 and MAP7D1 which regulate kinesin-1 recruitment to microtubules, interact with several DNA repair proteins including the double-stranded break repair proteins BRCA1 and RAD50. The interactions of MAP7 with BRCA1 and RAD50 are partly dependent on MAP7’s ability to bind phosphorylated Ser1336 in BRCA1 and phosphorylated Thr690 in RAD50. Using a phospho-specific antibody against BRCA1 pSer1336, it was established that the kinase which phosphorylates BRCA1 at Ser1336 is casein kinase 2. Furthermore, co-immunoprecipitation and domain mapping experiments revealed that MAP7 interacts with the DNA repair proteins through amino acids 144 to 300 located in its N-terminus. Additionally, these experiments showed that other proteins bridge the interactions between MAP7 and the DNA damage response proteins. Experiments with siRNA-mediated down-regulation of MAP7 and MAP7D1 elucidated that decreased levels of MAP7 and MAP7D1 lead to increased phosphorylation of p53 at Ser15 after γ-irradiation treatment. Moreover, the down-regulation of MAP7D1 leads to a strong G1 phase cell cycle arrest. The knock-down of both MAP7 and MAP7D1 in cells arrested in the G1 phase negatively affects DNA double-stranded break repair and the localisation of 53BP1 to the site of damage. In addition, cells with depleted MAP7 or MAP7D1 exhibit decreased localisation of RAD50 to the chromatin before and after γ-irradiation treatment. Taken together, these findings describe for the first time a novel function of MAP7 and MAP7D1 in the cellular response to DNA damage caused by γ-irradiation. | en_US |
