BLAP18/RMI2, a novel OB-fold-containing protein, is an essential component of the Bloom helicase-double Holliday junction dissolvasome.

Abstract

Bloom Syndrome is an autosomal recessive cancer-prone disorder caused by mutations in the BLM gene. BLM encodes a DNA helicase of the RECQ family, and associates with Topo IIIalpha and BLAP75/RMI1 (BLAP for BLM-associated polypeptide/RecQ-mediated genome instability) to form the BTB (BLM-Topo IIIalpha-BLAP75/RMI1) complex. This complex can resolve the double Holliday junction (dHJ), a DNA intermediate generated during homologous recombination, to yield noncrossover recombinants exclusively. This attribute of the BTB complex likely serves to prevent chromosomal aberrations and rearrangements. Here we report the isolation and characterization of a novel member of the BTB complex termed BLAP18/RMI2. BLAP18/RMI2 contains a putative OB-fold domain, and several lines of evidence suggest that it is essential for BTB complex function. First, the majority of BLAP18/RMI2 exists in complex with Topo IIIalpha and BLAP75/RMI1. Second, depletion of BLAP18/RMI2 results in the destabilization of the BTB complex. Third, BLAP18/RMI2-depleted cells show spontaneous chromosomal breaks and are sensitive to methyl methanesulfonate treatment. Fourth, BLAP18/RMI2 is required to target BLM to chromatin and for the assembly of BLM foci upon hydroxyurea treatment. Finally, BLAP18/RMI2 stimulates the dHJ resolution capability of the BTB complex. Together, these results establish BLAP18/RMI2 as an essential member of the BTB dHJ dissolvasome that is required for the maintenance of a stable genome.

• Authors: Thiyam Ramsing Singh, Abdullah Mahmood Ali, Valeria Busygina, Steven Raynard, Qiang Fan, Chang-hu Du, Paul R Andreassen, Patrick Sung, Amom Ruhikanta Meetei
• Journal: Genes & development (Genes Dev) Vol. 22 Issue 20 Pg. 2856-68 (Oct 15 2008) ISSN: 0890-9369 [Print] United States
• PMID: 18923083 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Carrier Proteins
• Chromatin
• DNA, Cruciform
• DNA-Binding Proteins
• Nuclear Proteins
• Oligonucleotides
• RMI1 protein, human
• RMI2 protein, human
• RNA, Small Interfering
• Recombinant Proteins
• Bloom syndrome protein
• DNA Helicases
• RecQ Helicases
• DNA Topoisomerases, Type I
• Hydroxyurea

Topics

• Amino Acid Sequence
• Animals
• Bloom Syndrome (metabolism)
• Bone Neoplasms (genetics, metabolism, pathology)
• Carrier Proteins (chemistry, genetics, metabolism)
• Cell Nucleus (metabolism)
• Cells, Cultured
• Chickens
• Chromatin (genetics, metabolism)
• Chromatography, Affinity
• Chromosome Breakage
• Computational Biology
• DNA Helicases (chemistry, physiology)
• DNA Repair
• DNA Replication (drug effects)
• DNA Topoisomerases, Type I (physiology)
• DNA, Cruciform (genetics, metabolism)
• DNA-Binding Proteins (antagonists & inhibitors, genetics, metabolism)
• Fibrosarcoma (genetics, metabolism, pathology)
• HeLa Cells
• Humans
• Hydroxyurea (pharmacology)
• Kidney (cytology, drug effects, metabolism)
• Microscopy, Fluorescence
• Mitosis
• Molecular Sequence Data
• Nuclear Proteins (antagonists & inhibitors, chemistry, genetics, metabolism)
• Oligonucleotides (chemistry, genetics, metabolism)
• Osteosarcoma (genetics, metabolism, pathology)
• Phosphorylation (drug effects)
• Protein Folding
• RNA, Small Interfering (pharmacology)
• RecQ Helicases
• Recombinant Proteins (genetics, isolation & purification, metabolism)
• Sequence Homology, Amino Acid