Inactivation of the Nuclear Receptor Coactivator RAP250 in Mice Results in Placental Vascular Dysfunction

Abstract

Coactivators constitute a diverse group of proteins that are essential for optimal transcriptional activity of nuclear receptors. In the past few years many coactivators have been identified but it is still unclear whether these proteins interact indiscriminately with all nuclear receptors and whether there is some redundancy in their functions. We have previously cloned and characterized RAP250 (ASC-2/PRIP/TRBP/NRC), an LXXLLcontaining coactivator for nuclear receptors. In order to study its biological role, Rap250 null mice were generated by gene targeting. Here we show that genetic disruption of Rap250 results in embryonic lethality at embryonic day (E) 13.5. Histological examination of placentas revealed a dramatically reduced spongiotrophoblast layer, a collapse of blood vessels in the region bordering the spongiotrophoblast, and labyrinthine layers in placentas from Rap250 ؊/؊ embryos. These findings suggest that the lethality of Rap250 ؊/؊ embryos is the result of obstructed placental blood circulation. Moreover, the transcriptional activity of PPAR␥ is reduced in fibroblasts derived from Rap250 ؊/؊ embryos, suggesting that RAP250 is an essential coactivator for this nuclear receptor in the placenta. Our results demonstrate that RAP250 is necessary for placental development and thus essential for embryonic development.Nuclear receptors comprise a family of transcription factors that regulate gene expression in a ligand-dependent manner. Upon ligand binding these proteins activate transcription of specific genes involved in the control of diverse physiological processes, such as cellular growth, development, differentiation, and homeostasis (20). Binding of ligands to the ligandbinding domain of nuclear receptors causes conformational changes of the receptor, enabling the recruitment of coactivators harboring LXXLL motifs (see below). A number of coactivators for nuclear receptors have been identified (for a review, see reference 6). Among the most studied is the steroid receptor coactivator 1 (SRC-1) family, which contains three related coactivators, referred to as SRC-1, SRC-2/GRIP1/ TIF2, and SRC-3/p/CIP/RAC3/ACTR/AIB1/TRAM1 (1,4,7,17,23,28,30,33). These factors, together with CBP/p300 and pCAF, bind nuclear receptors and gain access to target promoter regions through histone acetyltransferase-mediated nucleosome remodeling. Another class of coactivators is represented by the TRAP/DRIP/ARC multiprotein complex (5, 22, 26), with one major nuclear receptor interacting subunit, PBP/ TRAP220/DRIP205 (25,31,41,45), that appears to act independently of histone acetyltransferase activity.Nuclear receptor-activating protein 250 (RAP250) (3), also called ASC-2, PRIP, TRBP, and NRC (13,15,19,42), was recently cloned and described as a novel nuclear receptor coactivator which interacts with the ligand-binding domain of ligand-bound nuclear receptors. The interaction is mediated through a short hydrophobic motif called the LXXLL motif (or NR box) which is found in most nuclear receptor coactivators. In contrast to ...

Haploid Inactivation of the Amplified-in-Breast Cancer 3 Coactivator Reduces the Inhibitory Effect of Peroxisome Proliferator-Activated Receptor γ and Retinoid X Receptor on Cell Proliferation and Accelerates Polyoma Middle-T Antigen-Induced Mammary Tumorigenesis in Mice

“…We and others have shown that inactivation of both of the AIB3 alleles in mice results in embryonic lethality due to defects in placental, cardiac, and hepatic development (23)(24)(25). These phenotypes are similar to those encountered in mice lacking PPAR␥ or PPAR␥-binding protein (26,27).…”

Gene amplification and associated loss of 5′ regulatory sequences of CoAA in human cancers

“…TRBP stimulates nuclear receptor-mediated gene activation and interacts with multiple components of the transcription complex. Genetic deletion of TRBP in mice is embryonically lethal, with severe defects in embryonic development (Kuang et al, 2002;Antonson et al, 2003). CoAA has been shown to synergistically activate transcription with TRBP and participate in the regulation of alternative splicing decisions (Auboeuf et al, 2004(Auboeuf et al, , 2005.…”

The Nuclear Hormone Receptor Coactivator NRC Is a Pleiotropic Modulator Affecting Growth, Development, Apoptosis, Reproduction, and Wound Repair

“…In addition to NRs, NRC also activates a variety of other transcription factors, such as c-Fos and c-Jun (31,34,40,41). Mice null for expression of NRC have been recently reported by three different laboratories (2,32,73). Deletion of the NRC gene in mice revealed that null mutants (NRC Ϫ/Ϫ ) die during early stages of embryogenesis (9.75 to 13.5 dpc) while mice heterozygous for the NRC gene (NRC ϩ/Ϫ ) in a mixed genetic background (C57/129) appear to be normal in growth and development.…”

“…The following findings summarize these results. CBP Ϫ/Ϫ , p300 Ϫ/Ϫ , TRAP220 Ϫ/Ϫ , and NRC Ϫ/Ϫ mice are embryonic lethal (2,20,26,32,33,57,68,73). TRAP220 ϩ/Ϫ mice are viable but exhibit pituitary hypothyroidism.…”

“…Deletion of the NRC gene in mice revealed that null mutants (NRC Ϫ/Ϫ ) die during early stages of embryogenesis (9.75 to 13.5 dpc) while mice heterozygous for the NRC gene (NRC ϩ/Ϫ ) in a mixed genetic background (C57/129) appear to be normal in growth and development. Intrauterine death of NRC-null embryos has been attributed to placental dysfunction, cardiac hypoplasia, and liver dysfunction, among other changes (2,32,73). Null PRIP MEFs in culture also fail to undergo adipocyte differentiation (53).…”