CCAAT/enhancer binding protein alpha assembles essential cooperating factors in common subnuclear domains.
The transcription factor CCAAT/enhancer binding protein alpha (C/EBP alpha) is the DNA binding subunit of a multiprotein complex that regulates the pituitary-specific GH promoter. C/EBP alpha is absent from the GHFT1-5 pituitary progenitor cell line in which ectopic C/EBP alpha expression leads to activation of the otherwise dormant GH promoter. Transcriptional regulatory complexes are commonly envisaged as assembling from components that evenly diffuse throughout the nucleoplasm. We show that C/EBP alpha, expressed in GHFT1-5 cells as a fusion with color variants of the green fluorescent protein (GFP), concentrated specifically at peri-centromeric chromosomal domains. Although we found the CREB-binding protein (CBP) to activate C/EBP alpha-dependent transcription, CBP was absent from the pericentromeric chromatin. C/EBP alpha expression was accompanied by the translocation of endogenous and ectopically expressed CBP to pericentromeric chromatin. The intranuclear recruitment of CBP required the transcriptional activation domains of C/EBP alpha. C/EBP alpha also caused GFP-tagged TATA binding protein (TBP) to relocate to the Hoechst-stained domains. The altered intranuclear distribution of critical coregulatory factors defines complexes formed upon C/EBP alpha expression. It also identifies an organizational activity, which we label "intranuclear marshalling," that may regulate gene expression by determining the cooperative and antagonistic interactions available at specific nuclear sites.
Schaufele
F
F
Metabolic Research Unit and Department of Medicine, University of California, San Francisco, California 94143-0540, USA. freds@metabolic.ucsf.edu
Enwright
J F
JF
Wang
X
X
Teoh
C
C
Srihari
R
R
Erickson
R
R
MacDougald
O A
OA
Day
R N
RN
D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D050882:CREB-Binding Protein; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002503:Centromere / Q000737:chemistry / Q000378:metabolism; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015870:Gene Expression; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins; D013006:Growth Hormone / Q000235:genetics; D008164:Luminescent Proteins / Q000235:genetics; D051379:Mice; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D010902:Pituitary Gland; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000378:metabolism; D013234:Stem Cells; D035181:TATA-Box Binding Protein; D015534:Trans-Activators / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
D022763:CCAAT-Enhancer-Binding Protein-alpha; D002843:Chromatin; D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D035181:TATA-Box Binding Protein; D015534:Trans-Activators; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; D013006:Growth Hormone; D050882:CREB-Binding Protein; C494364:Crebbp protein, mouse