Characterization of a basic helix-loop-helix protein, ABF-1: nuclear localization, transcriptional properties, and interaction with Id-2.
The activated B-cell factor (ABF)-1 cDNA was initially isolated from Epstein-Barr virus (EBV)-infected B cells and codes for a DNA-binding protein belonging to the basic helix-loop-helix (bHLH) family of transcription factors. In this study, we characterized the nuclear localization signal of ABF-1, mapped two distinct transcriptional repression domains, and identified one ABF-1-interacting protein, Id-2. By examining the subcellular location of deletion mutants of ABF-1 fused to green fluorescent protein (GFP), critical regions involved in nuclear localization were determined. Analysis of GFP-tagged ABF-1 deletion mutants revealed two separate regions capable of directing nuclear localization. One region mapped to the N-terminal amino acids 71 to 103, whereas the second region localized to the C-terminal bHLH domain. Transient transfection of ABF-1 deletion mutants demonstrated that the N-terminal amino acids 1 to 40 and the bHLH domain function together to achieve maximum repression of E2A activity. Taken together, these results indicate that ABF-1 is a nuclear transcriptional repressor with two distinct regions that function in a synergistic fashion to attenuate E2A-mediated gene activation.
Wong
J
J
Department of Biology, University of the Pacific, Stockton, California 95211, USA.
Funes-Duran
M
M
Ahlberg
J
J
Round
J
J
O'Connell
R
R
Miller
R
R
Chen
E
E
Richmond
P A
PA
Vierra
C A
CA
D051792:Basic Helix-Loop-Helix Proteins; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D051797:Inhibitor of Differentiation Protein 2; D019913:Nuclear Localization Signals / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D051820:TCF Transcription Factors; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D051797:Inhibitor of Differentiation Protein 2; D019913:Nuclear Localization Signals; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D051820:TCF Transcription Factors; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors; C497450:ID2 protein, human; C112467:MSC protein, human; C544912:TCF7L1 protein, human