Limits...
Silencing and nuclear repositioning of the lambda5 gene locus at the pre-B cell stage requires Aiolos and OBF-1.

Karnowski A, Cao C, Matthias G, Carotta S, Corcoran LM, Martensson IL, Skok JA, Matthias P - PLoS ONE (2008)

Bottom Line: However, when both factors are eliminated simultaneously a block is uncovered at the transition between pre-B and immature B cells, indicating that these proteins exert a critical function in developing B lymphocytes.Strikingly, developmentally regulated nuclear repositioning of the lambda5 gene is impaired in pre-B cells lacking OBF-1 and Aiolos.These studies uncover a novel role for OBF-1 and Aiolos in controlling the transcription and nuclear organization of genes involved in pre-BCR function.

View Article: PubMed Central - PubMed

Affiliation: Friedrich Miescher Institute for Biomedical Research, Novartis Research Foundation, Basel, Switzerland.

ABSTRACT
The chromatin regulator Aiolos and the transcriptional coactivator OBF-1 have been implicated in regulating aspects of B cell maturation and activation. Mice lacking either of these factors have a largely normal early B cell development. However, when both factors are eliminated simultaneously a block is uncovered at the transition between pre-B and immature B cells, indicating that these proteins exert a critical function in developing B lymphocytes. In mice deficient for Aiolos and OBF-1, the numbers of immature B cells are reduced, small pre-BII cells are increased and a significant impairment in immunoglobulin light chain DNA rearrangement is observed. We identified genes whose expression is deregulated in the pre-B cell compartment of these mice. In particular, we found that components of the pre-BCR, such as the surrogate light chain genes lambda5 and VpreB, fail to be efficiently silenced in double-mutant mice. Strikingly, developmentally regulated nuclear repositioning of the lambda5 gene is impaired in pre-B cells lacking OBF-1 and Aiolos. These studies uncover a novel role for OBF-1 and Aiolos in controlling the transcription and nuclear organization of genes involved in pre-BCR function.

Show MeSH
OBF-1 binds to the λ5 promoter region in vivo.(A) Organization of the λ5 locus and partial sequence of the λ5 promoter region. Three putative octamer sites were identified in silico. (B) OBF-1 binds to the λ5 regulatory region. Binding of OBF-1 to three putative octamer sites (−769 to −776), (−2029 to −2036) and (−3557 to −3550) was tested by ChIP analysis. As negative controls, ChIP assays were performed with control IgGs, and control amplifications were done with a fragment of an intergenic region from chromosome 8 lacking any octamer site. Immunoprecipitated DNA was quantified by real time PCR. One representative experiment is presented.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2571989&req=5

pone-0003568-g005: OBF-1 binds to the λ5 promoter region in vivo.(A) Organization of the λ5 locus and partial sequence of the λ5 promoter region. Three putative octamer sites were identified in silico. (B) OBF-1 binds to the λ5 regulatory region. Binding of OBF-1 to three putative octamer sites (−769 to −776), (−2029 to −2036) and (−3557 to −3550) was tested by ChIP analysis. As negative controls, ChIP assays were performed with control IgGs, and control amplifications were done with a fragment of an intergenic region from chromosome 8 lacking any octamer site. Immunoprecipitated DNA was quantified by real time PCR. One representative experiment is presented.

Mentions: In mice the λ5 and VpreB genes are located on chromosome 16; VpreB1 and λ5 are separated by 4 kb and VpreB2 is located 1 Mb downstream of the VpreB1-λ5 locus. This region also contains a gene encoding the ubiquitously expressed TopoisomeraseIIIβ (Top3β) which is located only 1.5 kb upstream from VpreB1 (Figure 5A). Expression of the λ5 and VpreB genes is initiated by and dependent on the basic helix–loop–helix proteins E12 and E47 and on the zinc finger/helix-loop-helix early B-cell factor (EBF) [44]. Although there are indications for a direct interaction of Aiolos/Ikaros with the λ5 promoter/enhancer region [38], [45], no direct interaction of OBF-1 with the λ5 locus has been documented so far. Bioinformatics analysis using PROMO [46] revealed three putative octamer binding sites (Octamer 1: CTTTGCAT (−768 to −775), Octamer 2: GTTTGCAT (−2028 to −2035) and Octamer 3: ATGCAAAT (−3557 to −3550; consensus –ATTTGCAT-) in the λ5 5′ regulatory region [47] (Figure 5A).


Silencing and nuclear repositioning of the lambda5 gene locus at the pre-B cell stage requires Aiolos and OBF-1.

Karnowski A, Cao C, Matthias G, Carotta S, Corcoran LM, Martensson IL, Skok JA, Matthias P - PLoS ONE (2008)

OBF-1 binds to the λ5 promoter region in vivo.(A) Organization of the λ5 locus and partial sequence of the λ5 promoter region. Three putative octamer sites were identified in silico. (B) OBF-1 binds to the λ5 regulatory region. Binding of OBF-1 to three putative octamer sites (−769 to −776), (−2029 to −2036) and (−3557 to −3550) was tested by ChIP analysis. As negative controls, ChIP assays were performed with control IgGs, and control amplifications were done with a fragment of an intergenic region from chromosome 8 lacking any octamer site. Immunoprecipitated DNA was quantified by real time PCR. One representative experiment is presented.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2571989&req=5

pone-0003568-g005: OBF-1 binds to the λ5 promoter region in vivo.(A) Organization of the λ5 locus and partial sequence of the λ5 promoter region. Three putative octamer sites were identified in silico. (B) OBF-1 binds to the λ5 regulatory region. Binding of OBF-1 to three putative octamer sites (−769 to −776), (−2029 to −2036) and (−3557 to −3550) was tested by ChIP analysis. As negative controls, ChIP assays were performed with control IgGs, and control amplifications were done with a fragment of an intergenic region from chromosome 8 lacking any octamer site. Immunoprecipitated DNA was quantified by real time PCR. One representative experiment is presented.
Mentions: In mice the λ5 and VpreB genes are located on chromosome 16; VpreB1 and λ5 are separated by 4 kb and VpreB2 is located 1 Mb downstream of the VpreB1-λ5 locus. This region also contains a gene encoding the ubiquitously expressed TopoisomeraseIIIβ (Top3β) which is located only 1.5 kb upstream from VpreB1 (Figure 5A). Expression of the λ5 and VpreB genes is initiated by and dependent on the basic helix–loop–helix proteins E12 and E47 and on the zinc finger/helix-loop-helix early B-cell factor (EBF) [44]. Although there are indications for a direct interaction of Aiolos/Ikaros with the λ5 promoter/enhancer region [38], [45], no direct interaction of OBF-1 with the λ5 locus has been documented so far. Bioinformatics analysis using PROMO [46] revealed three putative octamer binding sites (Octamer 1: CTTTGCAT (−768 to −775), Octamer 2: GTTTGCAT (−2028 to −2035) and Octamer 3: ATGCAAAT (−3557 to −3550; consensus –ATTTGCAT-) in the λ5 5′ regulatory region [47] (Figure 5A).

Bottom Line: However, when both factors are eliminated simultaneously a block is uncovered at the transition between pre-B and immature B cells, indicating that these proteins exert a critical function in developing B lymphocytes.Strikingly, developmentally regulated nuclear repositioning of the lambda5 gene is impaired in pre-B cells lacking OBF-1 and Aiolos.These studies uncover a novel role for OBF-1 and Aiolos in controlling the transcription and nuclear organization of genes involved in pre-BCR function.

View Article: PubMed Central - PubMed

Affiliation: Friedrich Miescher Institute for Biomedical Research, Novartis Research Foundation, Basel, Switzerland.

ABSTRACT
The chromatin regulator Aiolos and the transcriptional coactivator OBF-1 have been implicated in regulating aspects of B cell maturation and activation. Mice lacking either of these factors have a largely normal early B cell development. However, when both factors are eliminated simultaneously a block is uncovered at the transition between pre-B and immature B cells, indicating that these proteins exert a critical function in developing B lymphocytes. In mice deficient for Aiolos and OBF-1, the numbers of immature B cells are reduced, small pre-BII cells are increased and a significant impairment in immunoglobulin light chain DNA rearrangement is observed. We identified genes whose expression is deregulated in the pre-B cell compartment of these mice. In particular, we found that components of the pre-BCR, such as the surrogate light chain genes lambda5 and VpreB, fail to be efficiently silenced in double-mutant mice. Strikingly, developmentally regulated nuclear repositioning of the lambda5 gene is impaired in pre-B cells lacking OBF-1 and Aiolos. These studies uncover a novel role for OBF-1 and Aiolos in controlling the transcription and nuclear organization of genes involved in pre-BCR function.

Show MeSH