Repression of human gamma-globin gene expression by a short isoform of the NF-E4 protein is associated with loss of NF-E2 and RNA polymerase II recruitment to the promoter.
Binding of the stage selector protein (SSP) to the stage selector element (SSE) in the human gamma-globin promoter contributes to the preferential expression of the gamma-gene in fetal erythroid cells. The SSP contains the transcription factor CP2 and an erythroid-specific partner, NF-E4. The NF-E4 gene encodes a 22-kDa polypeptide employing a non-AUG initiation codon. Antisera specific to NF-E4 detects this species and an additional 14 kDa protein, which initiates from an internal methionine. Enforced expression of p14 NF-E4 in the K562 fetal/erythroid cell line, and in primary erythroid cord blood progenitors, results in repression of gamma-gene expression. Biochemical studies reveal that p14 NF-E4 interacts with CP2, resulting in diminished association of CP2 with the SSE in chromatin immunoprecipitation assays. p45 NF-E2 recruitment to the gamma-promoter is also lost, resulting in a reduction in RNA polymerase II and TBP binding and a fall in promoter transcriptional activity. This effect is specific, as enforced expression of a mutant form of p14 NF-E4, which fails to interact with CP2, also fails to repress gamma-gene expression in K562 cells. These findings provide one potential mechanism that could contribute to the autonomous silencing of the human gamma-genes in adult erythroid cells.
Zhao
Quan
Q
Rotary Bone Marrow Research Laboratory, Royal Melbourne Hospital Research Foundation, Parkville, Australia.
Zhou
Wenlai
W
Rank
Gerhard
G
Sutton
Rosemary
R
Wang
Xi
X
Cumming
Helen
H
Cerruti
Loretta
L
Cunningham
John M
JM
Jane
Stephen M
SM
D015672:Erythroid Precursor Cells; D005312:Fetal Blood / Q000166:cytology / Q000502:physiology*; D020868:Gene Silencing / Q000502:physiology*; D005914:Globins / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D020014:K562 Cells; D050984:NF-E2 Transcription Factor, p45 Subunit / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014161:Transduction, Genetic / Q000379:methods
D050984:NF-E2 Transcription Factor, p45 Subunit; C494692:NFE2 protein, human; D020033:Protein Isoforms; D014157:Transcription Factors; C487821:transcription factor NF-E4, human; D005914:Globins; D012319:RNA Polymerase II