Leaky severe combined immunodeficiency and aberrant DNA rearrangements due to a hypomorphic RAG1 mutation (original) (raw)
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Immunity, 2002
in V(D)J recombination has remained elusive. The only known specific role for RAG2 is to increase the stability Berkeley, California 94720 2 Graduate Program in Immunology and specificity of interactions between RAG1 and the RSS (Akamatsu and Oettinger, 1998; Swanson and De-Johns Hopkins University School of Medicine Baltimore, Maryland 21205 siderio, 1998), but not through direct, sequence-specific interaction with DNA (Eastman et al., 1999; Mo et al., ; Swanson and Desiderio, 1998). Although all conserved acidic residues within RAG2 are dispensable for Durham, North Carolina 27710 catalytic activity of the RAG complex (Landree et al., 1999), several basic residues of RAG2 have been shown to be critical for the ability of the recombinase to form Summary and open coding-end hairpins in vitro (Qiu et al., 2001), as well as for DNA substrate recognition by RAG1/2 Previous in vitro studies defined the minimal regions of RAG1 and RAG2 essential for V(D)J recombination. complex (Fugmann and Schatz, 2001).
Journal of Allergy and Clinical Immunology, 2014
Background: V(D)J recombination takes place during lymphocyte development to generate a large repertoire of T-and B-cell receptors. Mutations in recombination-activating gene 1 (RAG1) and RAG2 result in loss or reduction of V(D) J recombination. It is known that different mutations in RAG genes vary in residual recombinase activity and give rise to a broad spectrum of clinical phenotypes. Objective: We sought to study the immunologic mechanisms causing the clinical spectrum of RAG deficiency. Methods: We included 22 patients with similar RAG1 mutations (c.519delT or c.368_369delAA) resulting in N-terminal truncated RAG1 protein with residual recombination activity but presenting with different clinical phenotypes. We studied precursor B-cell development, immunoglobulin and T-cell receptor repertoire formation, receptor editing, and B-and T-cell numbers.
RAG Represents a Widespread Threat to the Lymphocyte Genome
Cell, 2015
The RAG1 endonuclease, together with its cofactor RAG2, is essential for V(D)J recombination but is a potent threat to genome stability. The sources of RAG1 mis-targeting and the mechanisms that have evolved to suppress it are poorly understood. Here, we report that RAG1 associates with chromatin at thousands of active promoters and enhancers in the genome of developing lymphocytes. The mouse and human genomes appear to have responded by reducing the abundance of "cryptic" recombination signals near RAG1 binding sites. This depletion operates specifically on the RSS heptamer, whereas nonamers are enriched at RAG1 binding sites. Reversing this RAG-driven depletion of cleavage sites by insertion of strong recombination signals creates an ectopic hub of RAG-mediated V(D)J recombination and chromosomal translocations. Our findings delineate rules governing RAG binding in the genome, identify areas at risk of RAG-mediated damage, and highlight the evolutionary struggle to accom...
Three faces of recombination activating gene 1 (RAG1) mutations
Acta Microbiologica et Immunologica Hungarica, 2015
Severe combined immune deficiency (SCID) is a group of genetic disorder associated with development of T- and/or B-lymphocytes. Recombination-activating genes (RAG1/2) play a critical role on VDJ recombination process that leads to the production of a broad T-cell receptor (TCR) and B-cell receptor (BCR) repertoire in the development of T and B cells. RAG1/2 genes mutations result in various forms of primary immunodeficiency, ranging from classic SCID to Omenn syndrome (OS) to atypical SCID with such as granuloma formation and autoimmunity. Herein, we reported 4 patients with RAG1 deficiency: classic SCID was seen in two patients who presented with recurrent pneumonia and chronic diarrhoea, and failure to thrive. OS was observed in one patient who presented with chronic diarrhoea, skin rash, recurrent lower respiratory infections, and atypical SCID was seen in one patient who presented with Pyoderma gangrenosum (PG) and had novel RAG1 mutation.
Autoubiquitylation of the V(D)J recombinase protein RAG1
Proceedings of the National Academy of Sciences, 2003
V(D)J recombination, the rearrangement of gene segments to assemble Ig and T cell receptor coding regions, is vital to B and T lymphocyte development. Here, we demonstrate that the V(D)J recombinase protein RAG1 undergoes ubiquitylation in cells. In vitro , the RING finger domain of RAG1 acts as a ubiquitin ligase that mediates its own ubiquitylation at a highly conserved K residue in the RAG1 amino-terminal region. Ubiquitylation is best supported by a specific ubiquitin-conjugating enzyme, UbcH3/CDC34, and requires an intact RAG1 RING finger motif. Disruption of the RING finger and certain RAG1 N-terminal truncations are associated with immunodeficiency in human patients, suggesting that RAG1's ubiquitin ligase is required for its biological role in lymphocyte development.
RAG2's non-core domain contributes to the ordered regulation of V(D)J recombination
Nucleic Acids Research, 2008
Variable (diversity) joining [V(D)J] recombination of immune gene loci proceeds in an ordered manner with D to J portions recombining first and then an upstream V joins that recombinant. We present evidence that the non-core domain of recombination activating gene (RAG) protein 2 is involved in the regulation of recombinatorial order. In mice lacking the non-core domain of RAG2 the ordered rearrangement is disturbed and direct V to D rearrangements are 10-to 1000-times increased in tri-partite immune gene loci. Some forms of interchromosomal translocations between TCRb and TCRd D gene segments are also increased in the core RAG2 animals as compared with their wildtype (WT) counterparts. In addition, the concise use of proper recombination signal sequences (RSSs) appears to be disturbed in the core RAG2 mice as compared with WT RAG2 animals.
V(D)J Recombination Exploits DNA Damage Responses to Promote Immunity
Trends in genetics : TIG, 2017
It has been recognized for 40 years that the variable (diversity) joining [V(D)J] recombination-mediated assembly of diverse B and T lymphocyte antigen receptor (AgR) genes is not only essential for adaptive immunity, but also a risk for autoimmunity and lymphoid malignancies. Over the past few years, several studies have revealed that recombination-activating gene (RAG) endonuclease-induced DNA double-strand breaks (DSBs) transcend hazardous intermediates during antigen receptor gene assembly. RAG cleavage within the genomes of lymphocyte progenitors and immature lymphocytes regulates the expression of ubiquitous and lymphocyte-specific gene transcripts to control the differentiation and function of both adaptive and innate immune cell lineages. These unexpected discoveries raise important new questions that have broad implications for basic immunology research and the screening, diagnosis, and treatment of human immunological disease.
Molecular and Cellular Biology, 2000
The V(D)J recombination reaction is composed of multiple nucleolytic processing steps mediated by the recombination-activating proteins RAG1 and RAG2. Sequence analysis has suggested that RAG2 contains six kelch repeat motifs that are predicted to form a six-bladed -propeller structure, with the second -strand of each repeat demonstrating marked conservation both within and between kelch repeat-containing proteins. Here we demonstrate that mutations G95R and ⌬I273 within the predicted second -strand of repeats 2 and 5 of RAG2 lead to immunodeficiency in patients P1 and P2. Green fluorescent protein fusions with the mutant proteins reveal appropriate localization to the nucleus. However, both mutations reduce the capacity of RAG2 to interact with RAG1 and block recombination signal cleavage, therefore implicating a defect in the early steps of the recombination reaction as the basis of the clinical phenotype. The present experiments, performed with an extensive panel of site-directed mutations within each of the six kelch motifs, further support the critical role of both hydrophobic and glycine-rich regions within the second -strand for RAG1-RAG2 interaction and recombination signal recognition and cleavage. In contrast, multiple mutations within the variable-loop regions of the kelch repeats had either mild or no effects on RAG1-RAG2 interaction and hence on the ability to mediate recombination. In all, the data demonstrate a critical role of the RAG2 kelch repeats for V(D)J recombination and highlight the importance of the conserved elements of the kelch motif.
Blood, 2000
The proteins encoded by RAG1 and RAG2 can initiate gene recombination by site-specific cleavage of DNA in immunoglobulin and T-cell receptor (TCR) loci. We identified a new homozygous RAG1 gene mutation (631delT) that leads to a premature stop codon in the 5Ј part of the RAG1 gene. The patient carrying this 631delT RAG1 gene mutation died at the age of 5 weeks from an Omenn syndromelike T ؉ /B ؊ severe combined immunodeficiency disease. The high number of blood T-lymphocytes (55 ؋ 10 6 /mL) showed an almost polyclonal TCR gene rearrangement repertoire not of maternal origin. In contrast, B-lymphocytes and immunoglobulin gene rearrangements were hardly detectable. We showed that the 631delT RAG1 gene can give rise to an N-terminal truncated RAG1 protein, using an internal AUG codon as the translation start site.
Rag mutations reveal robust alternative end joining.
Mammalian cells repair DNA double-strand breaks (DSBs) through either homologous recombination or non-homologous end joining (NHEJ). V(D)J recombination, a cut-and-paste mechanism for generating diversity in antigen receptors, relies on NHEJ for repairing DSBs introduced by the Rag1-Rag2 protein complex. Animals lacking any of the seven known NHEJ factors are therefore immunodeficient. Nevertheless, DSB repair is not eliminated entirely in these animals: evidence of a third mechanism, 'alternative NHEJ', appears in the form of extremely rare V(D)J junctions and a higher rate of chromosomal translocations. The paucity of these V(D)J events has suggested that alternative NHEJ contributes little to a cell's overall repair capacity, being operative only (and inefficiently) when classical NHEJ fails. Here we find that removing certain portions of murine Rag proteins reveals robust alternative NHEJ activity in NHEJ-deficient cells and some alternative joining activity even in wild-type cells. We propose a two-tier model in which the Rag proteins collaborate with NHEJ factors to preserve genomic integrity during V(D)J recombination.