Rabbit Anti-Human RNF20 (a.a. 906-975) Polyclonal antibody

MLL (myeloid/lymphoid or mixed-lineage leukemia) rearrangements are frequent in therapy-related and childhood acute leukemia, and are associated with poor prognosis. The majority of the rearrangements fall within a 7.3-kb MLL breakpoint cluster region (MLLbcr), particularly in a 0.4-kb hotspot at the intron11-exon12 boundary. The underlying mechanisms are poorly understood, though multiple pathways including early apoptotic signaling, accompanied by high-order DNA fragmentation, have been implicated. We introduced the MLLbcr hotspot in an EGFP-based recombination reporter system and demonstrated enhancement of both spontaneous and genotoxic treatment-induced DNA recombination by the MLLbcr in various human cell types. We identified Endonuclease G (EndoG), an apoptotic nuclease, as an essential factor for MLLbcr-specific DNA recombination after induction of replication stress. We provide evidence for replication stress-induced nuclear accumulation of EndoG, DNA binding by EndoG as well as cleavage of the chromosomal MLLbcr locus in a manner requiring EndoG. We demonstrate additional dependency of MLLbcr breakage on ATM signaling to histone H2B monoubiquitinase RNF20, involved in chromatin relaxation. Altogether our findings provide a novel mechanism underlying MLLbcr destabilization in the cells of origin of leukemogenesis, with replication stress-activated, EndoG-mediated cleavage at the MLLbcr, which may serve resolution of the stalled forks via recombination repair, however, also permits MLL rearrangements.

Monoubiquitylation of histone H2B (H2Bub1), catalyzed by the heterodimeric ubiquitin ligase complex RNF20/40, regulates multiple molecular and biological processes. The addition of a large ubiquitin moiety to the small H2B is believed to change the biochemical features of the chromatin. H2B monoubiquitylation alters nucleosome stability, nucleosome reassembly and higher order compaction of the chromatin. While these effects explain some of the direct roles of H2Bub1, there is growing evidence that H2Bub1 can also regulate multiple DNA-templated processes indirectly, by recruitment of specific factors ("readers") to the chromatin. H2Bub1 readers mediate much of the effect of H2Bub1 on histone crosstalk, transcriptional outcome and probably other chromatin-related activities. Here we summarize the current knowledge about H2Bub1-specific readers and their role in various biological processes. (C) 2014 Elsevier B.V. All rights reserved.