A soluble transcription factor, Oct-1, is also found in the insoluble nuclear matrix and possesses silencing activity in its alanine-rich domain.
Expression of the human thyrotropin beta (hTSHbeta) gene is restricted to thyrotrophs, at least in part, by silencing. Using transient-transfection assays, we have localized a silencer element to a region between -128 and -480 bp upstream of the transcription initiation site. The silencing activity was overcome in a thyrotroph-specific manner by an unknown enhancer located in the sequences at -approximately 10000 to -1200 bp. The ubiquitous POU homeodomain protein Oct-1 recognized the A/T-rich silencer element at multiple sites in gel mobility shift assays and in vitro footprinting analyses. The silencing activity of Oct-1 was localized in its C-terminal alanine-rich domain, suggesting that Oct-1 plays a role in silencing of the hTSHbeta promoter. Further, a significant fraction of Oct-1 was shown to be associated with the nuclear matrix, and the hTSHbeta silencer region was tethered to a nuclear matrix of human cells in vivo, suggesting a possible role of the Oct-1-hTSHbeta silencer region interaction in chromatin organization.
Kim
M K
MK
Molecular and Cellular Endocrinology Branch, National Institute of Diabetes and Degestive and Kidney Diseases, Bethesda, Maryland 20892, USA.
Lesoon-Wood
L A
LA
Weintraub
B D
BD
Chung
J H
JH
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002451:Cell Compartmentation; D002478:Cells, Cultured; D004268:DNA-Binding Proteins; D015536:Down-Regulation; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000378:metabolism*; D051863:Host Cell Factor C1; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D015530:Nuclear Matrix / Q000378:metabolism*; D050811:Octamer Transcription Factor-1; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D012995:Solubility; D013329:Structure-Activity Relationship; D013972:Thyrotropin / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*
D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; C497693:Hcfc1 protein, mouse; D018398:Homeodomain Proteins; D051863:Host Cell Factor C1; D050811:Octamer Transcription Factor-1; D009838:Oligodeoxyribonucleotides; C494165:POU2F1 protein, human; C494166:Pou2f1 protein, mouse; C494168:Pou2f1 protein, rat; D012333:RNA, Messenger; D014157:Transcription Factors; D013972:Thyrotropin