Paired-like homeodomain transcription factors 1 and 2 regulate follicle-stimulating hormone beta-subunit transcription through a conserved cis-element.
Paired-like homeodomain transcription factors (PITX) regulate the activity of pituitary hormone-encoding genes. Here, we examined mechanisms through which the family of PITX proteins control murine FSH beta-subunit (Fshb) transcription. We observed that endogenous PITX1 and PITX2 isoforms from murine LbetaT2 gonadotrope cells could bind a highly conserved proximal cis-element. Transfection of PITX1 or PITX2C in heterologous cells stimulated both murine and human Fshb/FSHB promoter-reporter activities, and in both cases, mutation of the critical cis-element abrogated these effects. In homologous LbetaT2 cells, the same mutation decreased basal reporter activity and greatly reduced activin A-stimulated transcription from murine and human promoter-reporters. Transfecting dominant-negative forms of PITX1 or PITX2C or knocking down PITX1 or -2 expression by RNA interference in LbetaT2 cells inhibited murine Fshb transcription, confirming roles for endogenous PITX proteins. Both PITX1 and PITX2C interacted with Smad3 (an effector of the activin signaling cascade in these cells) in coprecipitation experiments, and the PITX binding site mutation greatly inhibited Smad2/3/4-stimulated Fshb transcription. In summary, both PITX1 and PITX2C regulate murine and human Fshb/FSHB transcription through a conserved cis-element in the proximal promoter. Furthermore, the data indicate both common and distinct mechanisms of PITX1 and PITX2C action.
Lamba
Pankaj
P
Department of Pharmacology and Therapeutics, McGill University, McIntyre Medical Sciences Building, Montreal, Quebec, Canada H3G 1Y6.
Khivansara
Vishal
V
D'Alessio
Ana C
AC
Santos
Michelle M
MM
Bernard
Daniel J
DJ
D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002843:Chromatin / Q000235:genetics / Q000502:physiology; D017124:Conserved Sequence; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics*; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008156:Luciferases / Q000235:genetics; D051379:Mice; D051761:Paired Box Transcription Factors / Q000235:genetics / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D012756:Sheep; D013552:Swine; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection; D000097577:Homeobox Protein PITX2
D002843:Chromatin; D037201:Follicle Stimulating Hormone, beta Subunit; D018398:Homeodomain Proteins; D008156:Luciferases; D051761:Paired Box Transcription Factors; D034741:RNA, Small Interfering; D014157:Transcription Factors; D000097577:Homeobox Protein PITX2; C101485:homeobox protein PITX1