Reversible mislocalization of a disease-associated MRE11 splice variant product

Abstract

Ataxia-telangiectasia (AT) and related disorders feature cancer predisposition, neurodegeneration, and immunodeficiency resulting from failure to respond to DNA damage. Hypomorphic mutations in MRE11 cause an AT-like disorder (ATLD) with variable clinical presentation. We have sought to understand how diverse MRE11 mutations may provide unique therapeutic opportunities, and potentially correlate with clinical variability. Here we have undertaken studies of an MRE11 splice site mutation that was found in two ATLD siblings that died of pulmonary adenocarcinoma at the young ages of 9 and 16. The mutation, termed MRE11 alternative splice mutation (MRE11ASM), causes skipping of a highly conserved exon while preserving the protein’s open reading frame. A new mouse model expressing Mre11ASM from the endogenous locus demonstrates that the protein is present at very low levels, a feature in common with the MRE11ATLD1 mutant found in other patients. However, the mechanisms causing low protein levels are distinct. MRE11ASM is mislocalized to the cytoplasm, in contrast to MRE11ATLD1, which remains nuclear. Strikingly, MRE11ASM mislocalization is corrected by inhibition of the proteasome, implying that the protein undergoes strict protein quality control in the nucleus. These findings raise the prospect that inhibition of poorly understood nuclear protein quality control mechanisms might have therapeutic benefit in genetic disorders causing cytoplasmic mislocalization.

O-GlcNAc transferase couples MRE11 to transcriptionally active chromatin to suppress DNA damage

“…Lectin pulldowns [ 18 ] and cell fractionation [ 15 ] were performed as previously reported, except the cytoplasmic and nuclear fractions were combined here. For O -GlcNAc immunoprecipitation, we combined two antibodies: RL2 (Abcam: ab2739) and CTD110.6 (Cell Signaling Technologies: 9875), and used Pierce Direct IP Kit (ThermoFisher Scientific) according to manufacturer’s protocol to prepare the biological triplicate samples for mass spectrometry (MS).…”

Post-Translational Modification of MRE11: Its Implication in DDR and Diseases

“…Given its essential role in the repair of DSBs, the germline missense mutations in genes encoding the MRN complex cause human genomic instability syndromes such as: Ataxia-Telangiectasialike disorder (ATLD, mutations in MRE11), Nijmegen breakage syndrome-like disorder (NBSLD, mutations in RAD50), and Nijmegen breakage syndrome (NBS, mutations in NBS1), respectively [11]. In addition to immunodeficiency, genomic instability, and hypersensitivity to radiation, cancer predisposition is one of marker symptoms for these syndromes [12][13][14]. Additionally, plenty of somatic mutations (Table 1), including missense, frameshift and stop code gained, of genes encoded in the MRN complex have been linked to many types of cancer, such as breast, ovarian, colorectal, gastric, and prostate cancers [15].…”