title: Deficiency in mammalian histone H2B ubiquitin ligase Bre1 (Rnf20/Rnf40) leads to replication stress and chromosomal instability.
abstract: Mammalian Bre1 complexes (BRE1A/B (RNF20/40) in humans and Bre1a/b (Rnf20/40) in mice) function similarly to their yeast homolog Bre1 as ubiquitin ligases in monoubiquitination of histone H2B. This ubiquitination facilitates methylation of histone H3 at K4 and K79, and accounts for the roles of Bre1 and its homologs in transcriptional regulation. Recent studies by others suggested that Bre1 acts as a tumor suppressor, augmenting expression of select tumor suppressor genes and suppressing select oncogenes. In this study, we present an additional mechanism of tumor suppression by Bre1 through maintenance of genomic stability. We track the evolution of genomic instability in Bre1-deficient cells from replication-associated double-strand breaks (DSB) to specific genomic rearrangements that explain a rapid increase in DNA content and trigger breakage-fusion-bridge cycles. We show that aberrant RNA-DNA structures (R-loops) constitute a significant source of DSBs in Bre1-deficient cells. Combined with a previously reported defect in homologous recombination, generation of R-loops is a likely initiator of replication stress and genomic instability in Bre1-deficient cells. We propose that genomic instability triggered by Bre1 deficiency may be an important early step that precedes acquisition of an invasive phenotype, as we find decreased levels of BRE1A/B and dimethylated H3K79 in testicular seminoma and in the premalignant lesion in situ carcinoma.
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California 94305, USA.
authors.forename: Sophia B
authors.initials: SB
authors.lastname: Chernikova
authors.forename: Olga V
authors.initials: OV
authors.lastname: Razorenova
authors.forename: John P
authors.initials: JP
authors.lastname: Higgins
authors.forename: Brock J
authors.initials: BJ
authors.lastname: Sishc
authors.forename: Monica
authors.initials: M
authors.lastname: Nicolau
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Dorth
authors.forename: Diana A
authors.initials: DA
authors.lastname: Chernikova
authors.forename: Shirley
authors.initials: S
authors.lastname: Kwok
authors.forename: James D
authors.initials: JD
authors.lastname: Brooks
authors.forename: Susan M
authors.initials: SM
authors.lastname: Bailey
authors.forename: John C
authors.initials: JC
authors.lastname: Game
authors.forename: J Martin
authors.initials: JM
authors.lastname: Brown
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D015153:Blotting, Western; D049109:Cell Proliferation; D043171:Chromosomal Instability / Q000235:genetics*; D053903:DNA Breaks, Double-Stranded; D055785:Gene Knockdown Techniques; D006801:Humans; D008297:Male; D051379:Mice; D060888:Real-Time Polymerase Chain Reaction; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D036121:Receptor, EphA3; D018239:Seminoma / Q000235:genetics / Q000378:metabolism; D013736:Testicular Neoplasms / Q000235:genetics / Q000378:metabolism; D046888:Tissue Array Analysis; D044767:Ubiquitin-Protein Ligases / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism
chemical_list: C506646:RNF20 protein, human; C571257:RNF20 protein, mouse; C413363:RNF40 protein, human; D044767:Ubiquitin-Protein Ligases; C491718:EPHA3 protein, human; D020794:Receptor Protein-Tyrosine Kinases; D036121:Receptor, EphA3