Recombination between fragile regions associated with chromosomal rearrangements in glioblastoma can be mediated by RAGs

The RAGs, comprising RAG1 and RAG2, catalyze V(D)J recombination by recognizing recombination-signal sequences (RSS). Glioblastoma, the aggressive brain cancer, has many oncogenic chromosomal alterations; however, the mechanism of their generation is largely unknown. Here, we report that RAGs are expressed in human glioblastoma cells at transcript and protein levels. RNA-seq data analysis confirmed the expression of RAGs in the majority of patients with glioma. Analysis of patient breakpoint sequences reveals cryptic RSS in regions undergoing rearrangements. Biochemical studies demonstrate that RAGs can bind and cleave cryptic RSS in fragile regions (AMY1B, CAMK2D, RN7SKP123-MTF2, DIPK1A, IRX5-IRX6), albeit at lower efficiency. Recombination assay using episomes harboring the fragile regions showed aberrant recombination in these regions, and the efficiency was significantly reduced in RAG1 ablated cells. Finally, we recapitulate the glioblastoma associated AMY1B and RN7SKP123-MTF2 chromosomal rearrangement using an extrachromosomal assay. Thus, the present study provides mechanistic insights into the generation of chromosomal aberrations associated with glioblastoma.