Southwestern histochemical localization of regulatory element binding proteins for rat anterior pituitary hormones.

点击翻译按钮获取中文摘要

For the activation or suppression of a gene, the formation of stable molecule complexes between regulatory elements (RE) of the gene and binding proteins for the regulatory elements is often a prerequisite (REBP). Pit-1/GHF-1 form complex with RE of growth hormone (GH) (GH-1) and activates rat GH gene and it also binds to RE of prolactin (PRL) (P1) and activates PRL gene. At the same time, the binding of GH gene promoter proximal repressor element binding protein (PREB) to GH gene promoter proximal repressor element (PRE) suppress GH gene. In GH3 cells in vitro and in sections of rat anterior pituitary, Pit-1/GHF-1 and PREB were localized by utilizing a newly introduced Southwestern histochemical method (SWH). Pit-1/GHF-1 protein, GH and PRL were localized by immunohistochemistry (IHC). Some tissue sections were used for the double staining by SWH and IHC.For the localization of REBP,oligodeoxynucleotides (oligo-DNAs) correspond to rat GH-1 (-89 and -70) and rat PRE (-169 and -152) were used. SWH revealed that Pit-1/GHF-1 was mainly found in nuclei of GH or PRL cells as well as in nuclei of some other cells except gonadotrophs, whereas nuclear localization of the PREB was mainly in PRL cells and some other cells except GH cells and gonadotrophs in the rat pituitary tissue sections. Cell nuclei positive for Pit-1/GHF-1 by SWH were also positive for Pit-1/GHF-1 proteins by IHC.In GH3 cells in vitro, the results similar to that seen in sections of anterior pituitary were found.Our findings support a notion that the formation of complex between GH-1 and Pit-1/GHF-1 is needed for the activation of GH gene and that the formation of complex between P1 and Pit-1/GHF-1 is needed for the activation of PRL gene. If appears that the formation of complex between PRE and PREB suppressed GH gene in PRL producing cells. A mechanism that suppresses PRL gene in GH producing cells remains to be investigated.