Transcription factor dosage affects changes in higher order chromatin structure associated with activation of a heterochromatic gene.
The mechanisms of transcriptional activation in heterochromatin were investigated by using FISH to directly visualize changes in chromatin organization during activation of a heterochromatic lambda5 transgene. A DNase I hypersensitive site was shown to relocate the transgene to the outside of the pericentromeric heterochromatin complex in the absence of transcription. Activation of transcription, which is dependent on the transcription factor EBF, occurs in a stochastic manner that resembles telomeric silencing in yeast, with the transcribed gene remaining closely associated with the heterochromatin complex. Reducing the dosage of EBF results in a reduced frequency of localization of the transgene to the outside of the heterochromatin complex and lower levels of transcription. These data provide evidence that transcription factors can initiate changes in higher order chromatin structure during the earliest stages of gene activation.
Lundgren
M
M
Gene Regulation and Chromatin Group MRC Clinical Sciences Centre Imperial College School of Medicine Hammersmith Hospital W12 ONN, London, United Kingdom.
Chow
C M
CM
Sabbattini
P
P
Georgiou
A
A
Minaee
S
S
Dillon
N
N
D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism; D002478:Cells, Cultured; D002503:Centromere / Q000648:ultrastructure; D002843:Chromatin / Q000737:chemistry* / Q000648:ultrastructure; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D003850:Deoxyribonuclease I / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D018628:Gene Dosage; D005786:Gene Expression Regulation; D006570:Heterochromatin / Q000648:ultrastructure; D017404:In Situ Hybridization, Fluorescence; D008677:Metaphase; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D008957:Models, Genetic; D010957:Plasmids / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D019076:Transgenes
D002843:Chromatin; D004268:DNA-Binding Proteins; C489921:Ebf1 protein, mouse; D006570:Heterochromatin; D015534:Trans-Activators; D014157:Transcription Factors; D012313:RNA; D004247:DNA; D003850:Deoxyribonuclease I