The immunoglobulin heavy chain super enhancer controls class switch recombination in developing B cells.

Class switch recombination (CSR) plays an important role in adaptive immune response by enabling mature B cells to replace the initial IgM by another antibody class (IgG, IgE or IgA). CSR is preceded by transcription of the IgH constant genes and is controlled by the super-enhancer 3' regulatory region (3'RR) in an activation-specific manner. The 3'RR is composed of four enhancers (hs3a, hs1-2, hs3b and hs4).

Stem cell-like reprogramming is required for leukemia-initiating activity in B-ALL.

B cell acute lymphoblastic leukemia (B-ALL) is a multistep disease characterized by the hierarchical acquisition of genetic alterations. However, the question of how a primary oncogene reprograms stem cell-like properties in committed B cells and leads to a preneoplastic population remains unclear. Here, we used the PAX5::ELN oncogenic model to demonstrate a causal link between the differentiation blockade, the self-renewal, and the emergence of preleukemic stem cells (pre-LSCs).

Switch Tandem Repeats Influence the Choice of the Alternative End-Joining Pathway in Immunoglobulin Class Switch Recombination.

Immunoglobulin class switch recombination (CSR) plays an important role in humoral imm\une responses by changing the effector functions of antibodies. CSR occurs between highly repetitive switch (S) sequences located upstream of immunoglobulin constant gene exons. Switch sequences differ in size, the nature of their repeats, and the density of the motifs targeted by the activation-induced cytidine deaminase (AID), the enzyme that initiates CSR.

Long-Range Control of Class Switch Recombination by Transcriptional Regulatory Elements.

Immunoglobulin class switch recombination (CSR) plays a crucial role in adaptive immune responses through a change of the effector functions of antibodies and is triggered by T-cell-dependent as well as T-cell-independent antigens. Signals generated following encounter with each type of antigen direct CSR to different isotypes. At the genomic level, CSR occurs between highly repetitive switch sequences located upstream of the constant gene exons of the immunoglobulin heavy chain locus.

Mechanism and regulation of class switch recombination by IgH transcriptional control elements.

Class switch recombination (CSR) plays an important role in humoral immunity by generating antibodies with different effector functions. CSR to a particular antibody isotype is induced by external stimuli, and occurs between highly repetitive switch (S) sequences. CSR requires transcription across S regions, which generates long non-coding RNAs and secondary structures that promote accessibility of S sequences to activation-induced cytidine deaminase (AID).

Recombination may occur in the absence of transcription in the immunoglobulin heavy chain recombination centre.

Developing B cells undergo V(D)J recombination to generate a vast repertoire of Ig molecules. V(D)J recombination is initiated by the RAG1/RAG2 complex in recombination centres (RCs), where gene segments become accessible to the complex. Whether transcription is the causal factor of accessibility or whether it is a side product of other processes that generate accessibility remains a controversial issue.

Essential role of the initial activation signal in isotype selection upon deletion of a transcriptionally committed promoter.

Class switch recombination (CSR), which targets exclusively the constant region of the immunoglobulin heavy chain (IgH) locus, plays an important role in humoral immunity by generating different antibody effector functions. The IgH constant locus contains multiple genes controlled by isotype (I) promoters induced by extracellular signals that activate specific I promoters, leading to B cell commitment. However, it is unknown whether after initial commitment to one promoter, non-responsive I promoters are irreversibly silent or if they can be activated after exposure to their specific inducers.

Two modes of -activation of switch transcription by the superenhancer.

B cell isotype switching plays an important role in modulating adaptive immune responses. It occurs in response to specific signals that often induce different isotype (I) promoters driving transcription of switch regions, located upstream of the Ig heavy chain () constant genes. The transcribed switch regions can recombine, leading to a change of the constant gene and, consequently, of antibody isotype.

Developmental regulation of DNA cytosine methylation at the immunoglobulin heavy chain constant locus.

DNA cytosine methylation is involved in the regulation of gene expression during development and its deregulation is often associated with disease. Mammalian genomes are predominantly methylated at CpG dinucleotides. Unmethylated CpGs are often associated with active regulatory sequences while methylated CpGs are often linked to transcriptional silencing.

PAX5-ELN oncoprotein promotes multistep B-cell acute lymphoblastic leukemia in mice.

is a well-known haploinsufficient tumor suppressor gene in human B-cell precursor acute lymphoblastic leukemia (B-ALL) and is involved in various chromosomal translocations that fuse a part of PAX5 with other partners. However, the role of PAX5 fusion proteins in B-ALL initiation and transformation is ill-known. We previously reported a new recurrent t(7;9)(q11;p13) chromosomal translocation in human B-ALL that juxtaposed to the coding sequence of elastin ().

Parallels between Mammalian Mechanisms of Monoallelic Gene Expression.

Different types of monoallelic gene expression are present in mammals, some of which are highly flexible, whereas others are more rigid. These include allelic exclusion at antigen receptor loci, the expression of olfactory receptor genes, genomic imprinting, X-chromosome inactivation, and random monoallelic expression (MAE). Although these processes play diverse biological roles, and arose through different selective pressures, the underlying epigenetic mechanisms show striking resemblances.

Duplication of a germline promoter downstream of the IgH 3' regulatory region impairs class switch recombination.

During an adaptive immune response, B cells can change their surface immunoglobulins from IgM to IgG, IgE or IgA through a process called class switch recombination (CSR). Switching is preceded by inducible non-coding germline transcription (GLT) of the selected constant gene(s), which is largely controlled by a super-enhancer called the 3' regulatory region (3'RR). Despite intense efforts, the precise mechanisms that regulate GLT are still elusive.

Inducible CTCF insulator delays the 3' regulatory region-mediated activation of germline promoters and alters class switching.

Class switch recombination (CSR) plays an important role in adaptive immune response by enabling mature B cells to switch from IgM expression to the expression of downstream isotypes. CSR is preceded by inducible germline (GL) transcription of the constant genes and is controlled by the 3' regulatory region (3'RR) in a stimulus-dependent manner. Why the 3'RR-mediated up-regulation of GL transcription is delayed to the mature B-cell stage is presently unknown.

Developmental Switch in the Transcriptional Activity of a Long-Range Regulatory Element.

Eukaryotic gene expression is often controlled by distant regulatory elements. In developing B lymphocytes, transcription is associated with V(D)J recombination at immunoglobulin loci. This process is regulated by remote cis-acting elements.

Complete cis Exclusion upon Duplication of the Eμ Enhancer at the Immunoglobulin Heavy Chain Locus.

Developing lymphocytes somatically diversify their antigen-receptor loci through V(D)J recombination. The process is associated with allelic exclusion, which results in monoallelic expression of an antigen receptor locus. Various cis-regulatory elements control V(D)J recombination in a developmentally regulated manner, but their role in allelic exclusion is still unclear.

Insertion of an imprinted insulator into the IgH locus reveals developmentally regulated, transcription-dependent control of V(D)J recombination.

The assembly of antigen receptor loci requires a developmentally regulated and lineage-specific recombination between variable (V), diversity (D), and joining (J) segments through V(D)J recombination. The process is regulated by accessibility control elements, including promoters, insulators, and enhancers. The IgH locus undergoes two recombination steps, D-J(H) and then V(H)-DJ(H), but it is unclear how the availability of the DJ(H) substrate could influence the subsequent V(H)-DJ(H) recombination step.

Quantification of V(D)J recombination by real-time quantitative PCR.

B and T lymphocytes have the unique capacity to somatically rearrange their antigen receptor loci through V(D)J recombination. D-JH and VH-DJH recombination events are usually visualized by semi-quantitative PCR followed by detection of end products, which is time consuming and requires the use of hazardous elements. Additionally, it necessitates relatively large amounts of genomic DNA which could be limiting when the cell populations of interest are rare.

Tissue-specific inactivation of HAT cofactor TRRAP reveals its essential role in B cells.

The transformation/transcription domain-associated protein (TRRAP) is a common component of many histone acetyltransferase (HAT) complexes. Targeted-deletion of the Trrap gene led to early embryonic lethality and revealed a critical function of TRRAP in cell proliferation. Here, we investigate the function of TRRAP in murine B cells.

Seeking sense of antisense switch transcripts.

In B lymphocytes, class switch recombination (CSR) machinery targets highly repetitive sequences, called switch (S) sequences, in the constant domain of the immunoglobulin heavy chain (IgH) locus. Cotranscriptional generation of R loops at S sequences provides the substrate for the mutagenic enzyme AID (Activation-Induced cytidine Deaminase), which initiates the DNA breaks at the transcribed sequences. Both sense and antisense transcripts across the S regions have been reported.

Sense transcription through the S region is essential for immunoglobulin class switch recombination.

Class switch recombination (CSR) occurs between highly repetitive sequences called switch (S) regions and is initiated by activation-induced cytidine deaminase (AID). CSR is preceded by a bidirectional transcription of S regions but the relative importance of sense and antisense transcription for CSR in vivo is unknown. We generated three mouse lines in which we attempted a premature termination of transcriptional elongation by inserting bidirectional transcription terminators upstream of Sμ, upstream of Sγ3 or downstream of Sγ3 sequences.

Combined deficiency of MSH2 and Sμ region abolishes class switch recombination.

Class switch recombination (CSR) is mediated by G-rich tandem repeated sequences termed switch regions. Transcription of switch regions generates single-stranded R loops that provide substrates for activation-induced cytidine deaminase. Mice deficient in MSH2 have a mild defect in CSR and analysis of their switch junctions has led to a model in which MSH2 is more critical for switch recombination events outside than within the tandem repeats.

Downstream class switching leads to IgE antibody production by B lymphocytes lacking IgM switch regions.

Ig heavy chain (IgH) class-switch recombination (CSR) replaces the IgH C mu constant region exons with one of several sets of downstream IgH constant region exons (e.g., C gamma, C epsilon, or C alpha), which affects switching from IgM to another IgH class (e.

Replacement of Imu-Cmu intron by NeoR gene alters Imu germ-line expression but has no effect on V(D)J recombination.

The NeoR gene has often been used to unravel the mechanisms underlying long-range interactions between promoters and enhancers during V(D)J assembly and class switch recombination (CSR) in the immunoglobulin heavy chain (IgH) locus. This approach led to the notion that CSR is regulated through competition of germ-line (GL) promoters for activities displayed by the 3' regulatory region (3'RR). This polarized long-range effect of the 3'RR is disturbed upon insertion of NeoR gene in the IgH constant (C(H)) region, where only GL transcription derived from upstream GL promoters is impaired.