BLyF, a novel cell-type- and stage-specific regulator of the B-lymphocyte gene mb-1

The mb-1 gene encodes an integral membrane protein that appears to be required for the surface expression and signalling function(s) of the immunoglobulin receptor on B lymphocytes. The gene is expressed in a lineage-restricted manner. It is activated early in B-cell ontogeny, continues to be expressed in mature B cells, but is turned off in terminally differentiated plasma cells. We have identified the mb-1 promoter and functionally tested its activity by transient transfections. A 737-bp promoter fragment preferentially stimulates accurately initiated transcription in mb-1-expressing B cells. Deletion analysis of the promoter suggests the presence of two functional domains, proximal and distal. Both domains independently activate transcription from a heterologous promoter. The distal domain functions in a cell-type- and stage-specific manner, activating transcription in B cells but not in T cells or plasma cells. A 25-bp element within this domain is necessary and sufficient for activity. This element is recognized by a novel cell-type- and stage-specific transcription factor termed BLyF. The binding of BLyF completely correlates with the ability of the regulatory element to stimulate transcription. Thus, BLyF appears to positively regulate transcription of the mb-1 gene. Our results also suggest that the inactivity of the mb-1 locus in plasma cells is not simply due to the loss of BLyF activity.

[1]  J. Sambrook,et al.  Molecular Cloning: A Laboratory Manual , 2001 .

[2]  R. Grosschedl,et al.  A novel lineage‐specific nuclear factor regulates mb‐1 gene transcription at the early stages of B cell differentiation. , 1991, The EMBO journal.

[3]  R. Grosschedl,et al.  Heterogeneously initiated transcription from the pre-B- and B-cell-specific mb-1 promoter: analysis of the requirement for upstream factor-binding sites and initiation site sequences , 1991, Molecular and cellular biology.

[4]  S. Smale,et al.  LyF-1, a transcriptional regulator that interacts with a novel class of promoters for lymphocyte-specific genes , 1991, Molecular and cellular biology.

[5]  M. Neuberger,et al.  The B-cell antigen receptor of the five immunoglobulin classes , 1991, Nature.

[6]  M. Kimoto,et al.  Direct identification of the putative surface IgM receptor-associated molecule encoded by murine B cell-specific mb-1 gene. , 1991, Journal of Immunology.

[7]  M. Kimoto,et al.  Signal transmission through the B cell-specific MB-1 molecule at the pre-B cell stage. , 1991, International immunology.

[8]  M. Kimoto,et al.  Structure of the murine mb-1 gene encoding a putative sIgM-associated molecule. , 1990, Journal of immunology.

[9]  A. Barberis,et al.  A novel B-cell lineage-specific transcription factor present at early but not late stages of differentiation. , 1990, Genes & development.

[10]  M. Klemsz,et al.  The macrophage and B cell-specific transcription factor PU.1 is related to the ets oncogene , 1990, Cell.

[11]  M. Reth,et al.  Molecular components of the B-cell antigen receptor complex of the IgM class , 1990, Nature.

[12]  K. S. Campbell,et al.  B lymphocyte antigen receptors (mIg) are non‐covalently associated with a disulfide linked, inducibly phosphorylated glycoprotein complex. , 1990, The EMBO journal.

[13]  R. Wall,et al.  Immunoglobulin enhancer and promoter motifs 5' of the B29 B-cell-specific gene. , 1989, Proceedings of the National Academy of Sciences of the United States of America.

[14]  W. Schaffner,et al.  A cloned octamer transcription factor stimulates transcription from lymphoid–specific promoters in non–B cells , 1988, Nature.

[15]  F. Melchers,et al.  B lymphocyte lineage‐restricted expression of mb‐1, a gene with CD3‐like structural properties. , 1988, The EMBO journal.

[16]  K. Rajewsky,et al.  A novel 34‐kd protein co‐isolated with the IgM molecule in surface IgM‐expressing cells. , 1988, The EMBO journal.

[17]  P. Sharp,et al.  Molecular cloning of an enhancer binding protein:Isolation by screening of an expression library with a recognition site DNA , 1988, Cell.

[18]  G. Schaffner,et al.  OVEC, a versatile system to study transcription in mammalian cells and cell-free extracts. , 1987, Nucleic acids research.

[19]  F. Melchers,et al.  A second gene, VpreB in the lambda 5 locus of the mouse, which appears to be selectively expressed in pre‐B lymphocytes. , 1987, The EMBO journal.

[20]  F. Melchers,et al.  λ5, a new light-chain-related locus selectively expressed in pre-B lymphocytes , 1986, Nature.

[21]  P. Sharp,et al.  A nuclear factor that binds to a conserved sequence motif in transcriptional control elements of immunoglobulin genes , 1986, Nature.

[22]  R. Grosschedl,et al.  Cell-type specificity of iminunoglobulin gene expression is regulated by at least three DNA sequence elements , 1985, Cell.