Creation of Estrogen Resistance in Vivo by Transgenic Overexpression of the Heterogeneous Nuclear Ribonucleoprotein-Related Estrogen Response Element Binding Protein

Abstract

Estrogen unresponsiveness among primate species can result from overexpression of a heterogeneous nuclear ribonucleoprotein (hnRNP) that competes with estrogen receptor (ER) for binding to the estrogen-response element (ERE). This hnRNP has been coined the "ERE-binding protein" (ERE-BP). The ERE-BP is a member of the hnRNP C-like subfamily of hnRNPs, traditionally considered to be single-strand RNA binding proteins designed for the stabilization and handling of pre-mRNA. To verify in vivo the dominant-negative actions of the ERE-BP to inhibit ER-ERE-directed transactivation and to avoid the potential for lethality from global overexpression of an hnRNP, we generated transgenic mice that overexpressed ERE-BP in breast tissue under the control of a whey acidic protein gene promoter. Graded overexpression of ERE-BP in transgenic mice was established. Founders were viable and fertile. Female transgenics in all lines gave birth to pups, but their ability to nurse was dependent on the level of ERE-BP expression in breast; high-ERE-BP expressors were unable to lactate. A gradient of impaired breast pheno(histo)type, from near normal to failed ductal development and lactational capacity, correlated with the relative level of transgene expression. ERE-BP, expressed either endogenously as a transgene or after transfection, colocalized with ERalpha in the nucleus of target cells. This work confirms that tissue-targeted overexpression of the ERE-BP can effectively block estrogen-ERalpha-ERE-directed action in vivo.

Heterogeneous nuclear ribonucleoprotein A/B and G inhibits the transcription of gonadotropin-releasing-hormone 1

“…Moreover, some of the hormone response elements and putative hnRNP-A/B binding sites are located close to each other in GnRH1 upstream (especially mGnRH1) (Fig. 7B), implying an interaction between hnRNP-A/B and the hormone receptors which have been shown in other hnRNPs in regulating other genes (Chen et al, 2005;Eggert et al, 2001Eggert et al, , 1997Smidt et al, 1995).…”

“…hnRNP-U, have been identified as repressing glucocorticoid receptor (GR)-dependent transcription by interacting with GR (Eggert et al, 2001(Eggert et al, , 1997. hnRNP-C like protein, also called estrogen-response element binding protein (ERE-BP), was identified as a competitor of ER for ERE and can cause estrogen unresponsiveness (Chen et al, 2005). A previous work also showed that there is an association between hnRNP-G and hnRNP-C as shown by co-immunoprecipitation experiments (Choi et al, 1986;Soulard et al, 1991).…”

Functional Characterization of Heterogeneous Nuclear Ribonuclear Protein C1/C2 in Vitamin D Resistance

“…More recently, hnRNPs have been shown to be capable of binding DNA in both single- (16,17) and double-stranded formats (14,15). Acting in their capacity as double-stranded DNA-binding proteins, we have shown previously that individual hnRNPs may function as dominant-negative modulators of steroid hormone-mediated transcription by competing with the VDR-RXR (14,15) and the estrogen receptor (21)(22)(23) for VDRE and estrogen response element, respectively. Here we describe the isolation, purification, and cloning of the cDNA for the naturally occurring human retinoid X and vitamin D response element-binding protein (REBiP), which was shown to be hnRNP C1/C2.…”

Role of multi-hnRNP nuclear complex in regulation of tumor suppressor ANXA7 in prostate cancer cells

“…The overexpression of an hnRNP and an estrogen response (ERE)-binding protein, both of which compete with ER for binding to the ERE-element, has been shown to result in estrogen resistance in breast cancer (Chen et al, 2005). Similarly, the overrepresented multi-hnRNP-complex at ANXA7 promoter in PC3 could affect GR and AR binding to the GREF/ARE-elements.…”