Summary

Recombination activating protein 2

V-D-J recombination is the combinatorial process by which the huge range of immunoglobulin and T cell binding specificity is generated from a limited amount of genetic material. This process is synergistically activated by RAG1 and RAG2 in developing lymphocytes. Defects in RAG2 in humans are a cause of severe combined immunodeficiency B cell negative and Omenn syndrome.

Literature references

Oettinger MA, Schatz DG, Gorka C, Baltimore D; , Science 1990;248:1517-1523.: RAG-1 and RAG-2, adjacent genes that synergistically activate V(D)J recombination. PUBMED:2360047

InterPro entry IPR004321

The variable portion of the genes encoding immunoglobulins and T cell receptors are assembled from component V, D, and J DNA segments by a site-specific recombination reaction termed V(D)J recombination. V(D)J recombination is targeted to specific sites on the chromosome by recombination signal sequences (RSSs) that flank antigen receptor gene segments. The RSS consists of a conserved heptamer (consensus, 5'-CACAGTG-3') and nonamer (consensus, 5'-ACAAAAACC-3') separated by a spacer of either 12 or 23 bp. Efficient recombination occurs between a 12-RSS and a 23-RSS, a restriction known as the 12/23 rule.

V(D)J recombination can be divided into two phases, DNA cleavage and DNA joining. DNA cleavage requires two lymphocyte-specific factors, the products of the recombination activating genes, RAG1 and RAG2, which together recognise the RSSs and create double strand breaks at the RSS-coding segment junctions PUBMED:11961538. RAG-mediated DNA cleavage occurs in a synaptic complex termed the paired complex, which is constituted from two distinct RSS-RAG complexes, a 12-SC and a 23-SC (where SC stands for signal complex). The DNA cleavage reaction involves two distinct enzymatic steps, initial nicking that creates a 3'-OH between a coding segment and its RSS, followed by hairpin formation in which the newly created 3'-OH attacks a phosphodiester bond on the opposite DNA strand. This generates a blunt, 5' phosphorylated signal end containing all of the RSS elements, and a covalently sealed hairpin coding end.

The second phase of V(D)J recombination, in which broken DNA fragments are processed and joined, is less well characterised. Signal ends are typically joined precisely to form a signal joint, whereas joining of the coding ends requires the hairpin structure to be opened and typically involves nucleotide addition and deletion before formation of the coding joint. The factors involved in these processes include ubiquitously expressed proteins involved in the repair of DNA double strand breaks by nonhomologous end joining, terminal deoxynucleotidyl transferase, and Artemis protein.

In addition to their critical roles in RSS recognition and DNA cleavage, the RAG proteins may perform two distinct types of functions in the postcleavage phase of V(D)J. A structural function has been inferred from the finding that, after DNA cleavage in vitro, the DNA ends remain associated with the RAG proteins in a "four end" complex known as the cleaved signal complex. After release of the coding ends in vitro, and after coding joint formation in vivo, the RAG proteins remain in a stable signal end complex (SEC) containing the two signal ends. These postcleavage complexes may serve as essential scaffolds for the second phase of the reaction, with the RAG proteins acting to organise the DNA processing and joining events.

The second type of RAG protein-mediated postcleavage activity is the catalysis of phosphodiester bond hydrolysis and strand transfer reactions. The RAG proteins are capable of opening hairpin coding ends in vitro. The RAG proteins also show 3' flap endonuclease activity that may contribute to coding end processing/joining and can utilise the 3' OH group on the signal ends to attack hairpin coding ends (forming hybrid or open/shut joints) or virtually any DNA duplex (forming a transposition product).

Gene Ontology

Cellular component	nucleus (GO:0005634)
Molecular function	DNA binding (GO:0003677)
Biological process	DNA recombination (GO:0006310)

External database links

PANDIT:	PF03089
SYSTERS:	RAG2

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Alignments

There are various ways to view or download the sequence alignments that we store. You can use a sequence viewer to look at either the seed or full alignment for the family, or you can look at a plain text version of the sequence in a variety of different formats. More...

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Alignment:	Seed (6) Full (2910) NCBI (3157) Metagenomics
Viewer:

Formatting options

Alignment:	Seed (6) Full (2910)
Format:
Order:	Tree Alphabetical
Sequence:	Inserts lower case All upper case
Gaps:
Download/view:	Download View

Download options

Very large alignments can often cause problems for the formatting tool above. If you find that downloading or viewing a large alignment is problematic, you can also download a gzip-compressed, Stockholm-format file containing the seed or full alignment for this family.

You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

The main seed and full alignments are generated using sequences from the UniProt sequence database. However, we also generate alignments using sequences from the NCBI sequence database and the "metaseq" metagenomics dataset.

You can view alignments from these two additional datasets using the form above, or you can download alignments of NCBI or metagenomics sequences, as gzip-compressed files.

Pfam alignments:	Seed (6) Full (2910) NCBI (3157) Metagenomics
Full length sequences	Full-sequences (2910)

External links

MyHits provides a collection of tools to handle multiple sequence alignments. For example, one can refine a seed alignment (sequence addition or removal, re-alignment or manual edition) and then search databases for remote homologs using HMMER2.

HMM logo

HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...

Trees

This page displays the phylogenetic tree for this family. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed or full alignments.

Note: You can also download the data files for the seed, full, NCBI or metagenomics trees.

Curation and family details

This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.

Curation

Seed source:

Pfam-B_4702 (release 6.5)

Previous IDs:

none

Type:

Family

Author:

Griffiths-Jones SR

Number in seed:

6

Number in full:

2910

Average length of the domain:

291.20 aa

Average identity of full alignment:

58 %

Average coverage of the sequence by the domain:

99.56 %

HMM information

HMM build commands:

build method: hmmbuild -o /dev/null HMM SEED

search method: hmmsearch -Z 9421015 -E 1000 HMM pfamseq

Model details:

Parameter	Sequence	Domain
Gathering cut-off	19.4	19.4
Trusted cut-off	19.7	21.9
Noise cut-off	19.1	18.9

Model length:

528

Family (HMM) version:

7

Download:

download the raw HMM for this family

Species distribution

Tree controls

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The tree shows the occurrence of this domain across different species. More...

Species trees

We show the species tree in one of two ways. For smaller trees we try to show an interactive representation, which allows you to select specific nodes in the tree and view them as an alignment or as a set of Pfam domain graphics.

Unfortunately we have found that there are problems viewing the interactive tree when the it becomes larger than a certain limit. Furthermore, we have found that Internet Explorer can become unresponsive when viewing some trees, regardless of their size. We therefore show a text representation of the species tree when the size is above a certain limit or if you are using Internet Explorer to view the site.

If you are using IE you can still load the interactive tree by clicking the "Generate interactive tree" button, but please be aware of the potential problems that the interactive species tree can cause.

Interactive tree

For all of the domain matches in a full alignment, we count the number that are found on all sequences in the alignment. This total is shown in the purple box.

We also count the number of unique sequences on which each domain is found, which is shown in green. Note that a domain may appear multiple times on the same sequence, leading to the difference between these two numbers.

Finally, we group sequences from the same organism according to the NCBI code that is assigned by UniProt, allowing us to count the number of distinct sequences on which the domain is found. This value is shown in the pink boxes.

We use the NCBI species tree to group organisms according to their taxonomy and this forms the structure of the displayed tree. Note that in some cases the trees are too large (have too many nodes) to allow us to build an interactive tree, but in most cases you can still view the tree in a plain text, non-interactive representation. Those species which are represented in the seed alignment for this domain are highlighted.

You can use the tree controls to manipulate how the interactive tree is displayed:

show/hide the summary boxes
highlight species that are represented in the seed alignment
expand/collapse the tree or expand it to a given depth
select a sub-tree or a set of species within the tree and view them graphically or as an alignment
save a plain text representation of the tree

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Structures

For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the MSD group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the RAG2 domain has been found.

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Family: RAG2 (PF03089)

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