title: Functions of PIT1 in GATA2-dependent transactivation of the thyrotropin beta promoter.
abstract: Thyrotropin (TSH) is a heterodimer consisting of alpha and beta chains, and the beta chain (TSHbeta) is specific to TSH. The coexistence of two transcription factors, PIT1 and GATA2, is known to be essential for TSHbeta expression. Using kidney-derived CV1 cells, we investigated the role of PIT1 in the expression of Tshb gene. GATA2 Zn finger domain, which is known to recognize GATA-responsive elements (GATA-REs), is essential for cooperation by PIT1. Transactivation of TSHbeta promoter requires PIT1-binding site upstream to GATA-REs (PIT1-US), and the spacing between PIT1-US and GATA-REs strictly determines the cooperation between PIT1 and GATA2. Moreover, truncation of the sequence downstream to GATA-REs enabled GATA2 to transactivate the TSHbeta promoter without PIT1. The deleted region (nt -82/-52) designated as a suppressor region (SR) was considered to inhibit transactivation by GATA2. The cooperation of PIT1 with GATA2 was not conventional synergism but rather counteracted SR-induced suppression (derepression). The minimal sequence for SR was mapped to the 9 bp sequence downstream to GATA-REs. Electrophoretic mobility shift assay suggested that some nuclear factor exists in CV1 cells, which binds with SR and this interaction was blocked by recombinant PIT1. Our study indicates that major activator for the TSHbeta promoter is GATA2 and that PIT1 protects the function of GATA2 from the inhibition by SR-binding protein.
authors.affiliation: Department of Internal Medicine, Seirei Hamamatsu General Hospital, Hamamatsu, Shizuoka, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Kashiwabara
authors.forename: Shigekazu
authors.initials: S
authors.lastname: Sasaki
authors.forename: Akio
authors.initials: A
authors.lastname: Matsushita
authors.forename: Koji
authors.initials: K
authors.lastname: Nagayama
authors.forename: Kenji
authors.initials: K
authors.lastname: Ohba
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Iwaki
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Matsunaga
authors.forename: Shingo
authors.initials: S
authors.lastname: Suzuki
authors.forename: Hiroko
authors.initials: H
authors.lastname: Misawa
authors.forename: Keiko
authors.initials: K
authors.lastname: Ishizuka
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Oki
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002522:Chlorocebus aethiops; D004247:DNA / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D050989:GATA2 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D037322:Thyrotropin, beta Subunit / Q000235:genetics*; D050817:Transcription Factor Pit-1 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D015533:Transcriptional Activation / Q000235:genetics / Q000502:physiology*
chemical_list: D050989:GATA2 Transcription Factor; D037322:Thyrotropin, beta Subunit; D050817:Transcription Factor Pit-1; D004247:DNA