Characterization of ABF-1, a novel basic helix-loop-helix transcription factor expressed in activated B lymphocytes.
Proteins of the basic helix-loop-helix (bHLH) family are required for a number of different developmental pathways, including neurogenesis, lymphopoiesis, myogenesis, and sex determination. Using a yeast two-hybrid screen, we have identified a new bHLH transcription factor, ABF-1, from a human B-cell cDNA library. Within the bHLH region, ABF-1 shows a remarkable conservation with other HLH proteins, including tal-1, NeuroD, and paraxis. Its expression pattern is restricted to a subset of lymphoid tissues, Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines, and activated human B cells. ABF-1 is capable of binding an E-box element either as a homodimer or as a heterodimer with E2A. Furthermore, a heterodimeric complex containing ABF-1 and E2A can be detected in EBV-immortalized lymphoblastoid cell lines. ABF-1 contains a transcriptional repression domain and is capable of inhibiting the transactivation capability of E47 in mammalian cells. ABF-1 represents the first example of a B-cell-restricted bHLH protein, and its expression pattern suggests that ABF-1 may play a role in regulating antigen-dependent B-cell differentiation.
Massari
M E
ME
Department of Biology, University of California, San Diego, La Jolla, California 92093, USA.
Rivera
R R
RR
Voland
J R
JR
Quong
M W
MW
Breit
T M
TM
van Dongen
J J
JJ
de Smit
O
O
Murre
C
C
D017502:Adenovirus E2 Proteins / Q000378:metabolism; D000595:Amino Acid Sequence; D001402:B-Lymphocytes / Q000378:metabolism*; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D015723:Gene Library; D006367:HeLa Cells; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D012097:Repressor Proteins / Q000378:metabolism; D016415:Sequence Alignment; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D017502:Adenovirus E2 Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004247:DNA; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C112467:MSC protein, human