Significance of the Chromatin Structure in Expression of the Rat Prolactin Gene

Abstract

To elucidate the mechanisms underlying cell type-specific expression of the growth hormone (GH) and prolactin (PRL) genes, we used rat pituitary-derived cell lines producing exclusively GH (GC cells) or PRL (235 cells), and examined the following: expression of transcription factors essential for GH and/or PRL gene expression; promoter/enhancer activity of the GH and PRL genes transiently introduced by transfection; and chromatin structures of the GH and PRL genes. Even in PRL-nonproducing GC cells, the PRL promoter/enhancer was more active than the GH promoter, and the transcription factors, Pit-1 and estrogen receptor (ER), essential for PRL gene expression were functional. The PRL promoter/enhancer of GC cells was normal. On DNase I sensitivity analysis of the chromatin structure, two hypersensitive sites were detected in PRL gene chromatin of PRL-producing 235 cells but none in that of GC cells. It thus follows that the major reason for absence of the expression of the endogenous PRL gene in GC cells is neither the lack of transcription factors necessary for PRL gene expression nor an anomaly of the PRL gene itself, but that the chromatin structure of the PRL gene differs in PRL-nonproducing and -producing cells. It was shown in this study that neither Pit-1 nor ER is required for conversion of the structure of PRL gene chromatin to a DNase I-hypersensitive state.

The transactivation‐competent carboxyl‐terminal domain of AF‐9 is expressed within a sexually dimorphic transcript in rat pituitary

“…The association of AF-9 with a chromatin remodeling function is intriguing with regard to our identification of rAF-9 in the pituitary, because mammalian homologues of SWI/SNF components have been shown to act cooperatively with both glucocorticoid and estrogen receptors that mediate endocrine feedback actions within the pituitary (24,25). Furthermore, selective expression of rAF-9 in the AP is consistent in this respect with both tissue-specific SWI/SNF components in mammalian systems (26) and evidence of pituitary cell-specific chromatin structures that determine hormone gene expression (27). The transcriptional regulatory activity of carboxyl-terminal hAF-9 in heterologous systems was shown by Prasad et al (4) to be both cell-and promoter-specific.…”

Chromatin Structure of the Rat Somatotropin Gene Locus and Physical Linkage of the Rat Somatotropin Gene and Skeletal‐Muscle Sodium‐Channel Gene

“…GC and 235 cells were grown as described [23]. Buffalo rat liver-derived BRL cells were obtained from Riken Cell Bank (Tsukuba, Japan) and grown in Dulbecco's modified minimal essential medium containing 10% fetal bovine serum (JRH Biosciences).…”