MCL-1 Depletion Impairs DNA Double-Strand Break Repair and Reinitiation of Stalled DNA Replication Forks.
Myeloid cell leukemia 1 (MCL-1) is a prosurvival BCL-2 protein family member highly expressed in hematopoietic stem cells (HSCs) and regulated by growth factor signals that manifest antiapoptotic activity. Here we report that depletion of MCL-1 but not its isoform MCL-1S increases genomic instability and cell sensitivity to ionizing radiation (IR)-induced death. MCL-1 association with genomic DNA increased postirradiation, and the protein colocalized with 53BP1 foci. Postirradiation, MCL-1-depleted cells exhibited decreased γ-H2AX foci, decreased phosphorylation of ATR, and higher levels of residual 53BP1 and RIF1 foci, suggesting that DNA double-strand break (DSB) repair by homologous recombination (HR) was compromised. Consistent with this model, MCL-1-depleted cells had a reduced frequency of IR-induced BRCA1, RPA, and Rad51 focus formation, decreased DNA end resection, and decreased HR repair in the DR-GFP DSB repair model. Similarly, after HU induction of stalled replication forks in MCL-1-depleted cells, there was a decreased ability to subsequently restart DNA synthesis, which is normally dependent upon HR-mediated resolution of collapsed forks. Therefore, the present data support a model whereby MCL-1 depletion increases 53BP1 and RIF1 colocalization at DSBs, which inhibits BRCA1 recruitment, and sensitizes cells to DSBs from IR or stalled replication forks that require HR for repair.
Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas, USA armattoo@houstonmethodist.org tpandita@houstonmethodist.org.
Abid R
AR
Mattoo
Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas, USA.
Raj K
RK
Pandita
Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas, USA.
Sharmistha
S
Chakraborty
Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas, USA.
Vijaya
V
Charaka
Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas, USA.
Kalpana
K
Mujoo
Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas, USA.
Clayton R
CR
Hunt
Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas, USA armattoo@houstonmethodist.org tpandita@houstonmethodist.org.
Tej K
TK
Pandita
D002467:Cell Nucleus / Q000378:metabolism / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D002843:Chromatin / Q000378:metabolism; D002869:Chromosome Aberrations; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004260:DNA Repair / Q000528:radiation effects; D004261:DNA Replication / Q000528:radiation effects; D042822:Genomic Instability / Q000528:radiation effects; D059765:Homologous Recombination / Q000528:radiation effects; D006801:Humans; D008954:Models, Biological; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000378:metabolism*; D011839:Radiation, Ionizing; D013312:Stress, Physiological / Q000528:radiation effects; D000071857:Tumor Suppressor p53-Binding Protein 1 / Q000378:metabolism
D002843:Chromatin; C579095:MCL1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D000071857:Tumor Suppressor p53-Binding Protein 1
53BP1; BCL-2; DSB repair; HR; ICL; MCL-1; apoptosis