Disease relevance of RAG1

• Amorphic mutations in the recombination activating genes RAG1 and RAG2 have been reported to cause T- B- SCID, whereas hypomorphic mutations led to the expansion of a few autoimmune T cell clones responsible for the Omenn syndrome phenotype [1].
• Human RAG2, like RAG1, is on chromosome 11 band p13 and therefore not linked to ataxia telangiectasia complementation groups [2].
• Epstein-Barr virus induction of recombinase-activating genes RAG1 and RAG2 [3].
• Expression of the recombination activating genes (RAG1 and RAG2) is not detectable in Epstein-Barr virus-associated human lymphomas [4].
• In this study we observed that administration of Toll-like receptor 9 (TLR9) agonists suppressed the severity of experimental colitis in RAG1-/- but not in SCID mice [5].

High impact information on RAG1

• Here we review the prevalence of autoantibodies in the initial antibody repertoire, their regulation by receptor editing, and the role of the recombinase proteins (RAG1 and RAG2) in this process [6].
• RAG1/2 catalyzes hairpin formation on target DNA adjacent to transposed RSS ends in a manner consistent with a model leading to chromosome translocations [7].
• Recombinant RAG1 protein greatly increases activity and complements an inactive extract from a RAG1 (-/-) pre-B cell line [8].
• PML contains a cysteine-rich region present in a new family of apparent DNA-binding proteins that includes a regulator of the interleukin-2 receptor gene (Rpt-1) and the recombination-activating gene product (RAG-1) [9].
• The expression of the V(D)J [variable (diversity) joining elements] recombination activating genes, RAG-1 and RAG-2, has been examined during T cell development in the thymus [10].

Chemical compound and disease context of RAG1

• Adherence of Acinetobacter calcoaceticus RAG-1 to human epithelial cells and to hexadecane [11].
• The oil-degrading Arthrobacter sp. RAG-1 produced an extracellular nondialyzable emulsifying agent when grown on hexadecane, ethanol, or acetate medium [12].

Biological context of RAG1

• We report here a novel clinical and immunological phenotype associated with recessive RAG1 hypomorphic mutations in 4 patients from 4 different families [1].
• A single promoter region was used for RAG1 transcription [13].
• Two new 5'-untranslated region (5'UTR) exons were identified in the human gene for the lymphocyte-specific endonuclease recombination activating gene-1 (RAG1) required for the somatic recombination yielding functional Ag receptors [14].
• We have characterized the genomic organization of the human RAG locus, mapped the transcriptional initiation sites, and partially sequenced and performed functional reporter assays on the 5' flanking regions of human RAG1 and RAG2 [13].
• Here we report the location of a human recombination activating gene (RAG2), in addition to RAG1, on chromosome 11, band p13, thereby formally demonstrating linkage of these genes in humans and showing that they are not linked to the known locus responsible for the A-T syndrome [2].

Anatomical context of RAG1

• We demonstrate that these peripheral blood neutrophils express variable and individual-specific TCRalphabeta repertoires and the RAG1/RAG2 recombinase complex [15].
• Notably, B cells expressing both RAG1 and RAG2 mRNA expressed only IgD mRNA, but not IgG mRNA [16].
• Promoter regions of human RAG1 and RAG2 are active in both lymphoid and nonlymphoid cell lines, suggesting that an outside regulatory element is probably involved in the tissue-specific transcriptional regulation of the RAG genes [13].
• In situ hybridization demonstrated jejunal cells expressing the new splice forms of RAG1 mRNA, both intraepithelially and in lamina propria [14].
• Flow cytometric and RT-PCR analysis of BALB/c and RAG1(-/-) mice splenocytes demonstrate that freshly isolated B cells, T cells, macrophages, and dendritic cells express both splice variant forms of ICOS ligand [17].

Associations of RAG1 with chemical compounds

• The extremely restricted T-cell repertoire and the lack of circulating B cells prompted analysis of the RAG1 gene, which revealed a novel homozygous thymine to cytosine substitution at nucleotide position 2686 [18].
• N-terminal RAG1 frameshift mutations in Omenn's syndrome: internal methionine usage leads to partial V(D)J recombination activity and reveals a fundamental role in vivo for the N-terminal domains [19].
• Separately from its role in V(D)J cleavage, the DDE motif of the RAG1/2 active site is specifically required for target DNA capture [20].
• These signal end complexes were distinct from various precleavage RAG1/2 signal complexes in that they were resistant to treatment with heparin [21].
• Here we subject RAG1, covalently cross-linked to DNA substrates, to partial cyanogen bromide degradation or trypsin proteolysis in order to map contacts on the protein [22].

Physical interactions of RAG1

• The presence of a methyl-CpG binding-domain protein inhibited the binding of the RAG1/RAG2 complex to all the methylated CpG sites that were tested [23].
• Intermediates in V(D)J recombination: a stable RAG1/2 complex sequesters cleaved RSS ends [21].

Regulatory relationships of RAG1

• In this study, we present evidence that activated mature CD5-positive human tonsil B cells coexpress both RAG1 and RAG2 mRNA and protein, and display DNA cleavage resulting from their recombinase activity [24].
• RAG-2 promotes heptamer occupancy by RAG-1 in the assembly of a V(D)J initiation complex [25].

Other interactions of RAG1

• During V(D)J recombination, the RAG1 and RAG2 proteins form a complex and initiate the process of rearrangement by cleaving between the coding and signal segments and generating hairpins at the coding ends [26].
• Rch1, a protein that specifically interacts with the RAG-1 recombination-activating protein [27].
• All 39 V(H) elements (with their adjacent heptamer/nonamer signal) were tested for site-specific cleavage with purified human core RAG1 and RAG2, and HMG1 proteins in a 12/23-coupled cleavage reaction [28].
• The contig spanning 8 Mb from RAG1 to KCNA4 has been assembled by STS and probe content mapping for 76 loci with an average spacing of about 100 kb [29].
• Expression of TdT and the lymphoid-associated genes Ig beta and RAG-1, but not PAX-5, was detected in this fraction, although at lower levels than in the IL-7R alpha+ progenitors [30].

Analytical, diagnostic and therapeutic context of RAG1

• We have investigated the molecular consequences of RAG1/2 expression in mature lymphocytes using a cell culture system (M12 and DR3) [31].
• Using the yeast two-hybrid assay, we have identified RCH1, a gene encoding a protein of molecular weight 58,000 that interacts specifically with RAG-1 [27].
• In this report, we use deletion mapping and site-directed mutagenesis to determine the minimal domains critical for interaction between RAG1 and RAG2 [32].
• Primers for first round and nested PCR of RAG1 and RAG2 were synthesized [33].
• This endonucleolytic activity was eliminated by immunoprecipitation using the RAG1-specific antibody, and required the 3'-hydroxy group [34].

References