The Hippo effector Yorkie activates transcription by interacting with a histone methyltransferase complex through Ncoa6. Qing Y 2014 et al.
The Hippo signaling pathway regulates tissue growth in Drosophila through the transcriptional coactivator Yorkie (Yki). How Yki activates target gene transcription is poorly understood. Here we identify Nuclear receptor coactivator 6 (Ncoa6), a subunit of the Trithorax-related (Trr) histone H3 lysine 4 (H3K4) methyltransferase complex, as a Yki-binding protein. Like Yki, Ncoa6 and Trr are functionally required for Hippo-mediated growth control and target gene expression. Strikingly, artificial tethering of Ncoa6 to Sd is sufficient to promote tissue growth and Yki target expression even in the absence of Yki, underscoring the importance of Yki-mediated recruitment of Ncoa6 in transcriptional activation. Consistent with the established role for the Trr complex in histone methylation, we show that Yki, Ncoa6 and Trr are required for normal H3K4 methylation at Hippo target genes. These findings shed light on Yki-mediated transcriptional regulation and uncover a potential link between chromatin modification and tissue growth.
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Ligand-induced transcriptional activation of gene expression by nuclear receptors is dependent on recruitment of coactivators as intermediary factors. Caira F et al 2000 describes the cloning and characterization of RAP250, a novel human nuclear receptor coactivator. The results of in vitro and in vivo experiments indicate that the interaction of RAP250 with nuclear receptors is ligand-dependent or ligand-enhanced depending on the nuclear receptor and involves only one short LXXLL motif called nuclear receptor box. Transient transfection assays further demonstrate that RAP250 has a large intrinsic glutamine-rich activation domain and can significantly enhance the transcriptional activity of several nuclear receptors, acting as a coactivator. Interestingly, Northern blot and in situ hybridization analyses reveal that RAP250 is widely expressed with the highest expression in reproductive organs (testis, prostate and ovary) and brain:,
NCBI Summary:
The protein encoded by this gene is a transcriptional coactivator that can interact with nuclear hormone receptors to enhance their transcriptional activator functions. This protein has been shown to be involved in the hormone-dependent coactivation of several receptors, including prostanoid, retinoid, vitamin D3, thyroid hormone, and steroid receptors. Alternatively spliced transcript variants encoding different isoforms have been described for this gene. [provided by RefSeq, Jun 2011]
General function
Nucleic acid binding, DNA binding, Transcription factor
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Cellular localization
Nuclear
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Ovarian function
Follicle development
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Expression regulated by
LH
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Ovarian localization
Granulosa, Luteal cells
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Liu DL, et al 2002 reported the expression and localization of RAP250 mRNA in rat ovary and possible implications in follicular development and ovulation.
The expression levels of nuclear receptor coregulators in specific tissue compartments and cells are thought to influence the expression of hormone-responsive genes involved in metabolism, development, and reproduction. RAP250 is a novel nuclear receptor coactivator highly expressed in brain and reproductive organs. To investigate the possible involvement of RAP250 in tissue-specific regulation of ovarian function, untreated immature, pregnant mare's serum gonadotropin luteinizing hormone (PMSG-LH)-primed, cycling, and pregnant rat models were used to study the localization and expression of RAP250 mRNA in rat ovary by in situ hybridization (ISH) and reverse transcriptase polymerase chain reaction (RT-PCR). The results showed that RAP250 mRNA was primarily localized to granulosa cells of healthy follicles in immature, cycling, and pregnant rats and increased during PMSG-induced follicular development. In the preovulatory and ovulatory follicles from the LH-primed rats of 48-h post-PMSG administration, the signals for RAP250 mRNA increased further and remained high until early luteal formation. Only a subset of corpora lutea during diestrus 1, diestrus 2, and initiation of pregnancy was weakly positive, and atretic follicles were largely negative. The RT-PCR results confirmed the presence of RAP250 mRNA in the rat ovary and strengthen the data from ISH. These findings suggest that RAP250 may play potential roles in follicular development and ovulation.
Follicle stages
Antral, Preovulatory, Corpus luteum
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Zhang H, et al 2003 reported spatial distribution of the messenger ribonucleic Acid and protein of the nuclear receptor coactivator, amplified in breast cancer-3, in mice.
Transcriptional activities of nuclear receptors are modulated by coactivators and corepressors. The amplified in breast cancer-3 protein (AIB3, also known as ASC-2, RAP250, PRIP, TRBP, and NCR) is a newly identified nuclear receptor coactivator that is amplified and overexpressed in breast cancers. This study aims to investigate the spatial expression of AIB3 mRNA and protein in various murine tissues. Quantitative measurements revealed that the concentrations of AIB3 mRNA differ substantially in different tissues in a descending order from the following: testis, brain, thymus, white fat, pituitary, ovary, adrenal gland, lung, uterus, kidney, heart, skeletal muscle, liver, and virgin mammary gland. The AIB3 mRNA level in the testis is 165-fold higher than that in the virgin mammary gland. Specific antiserum was generated and used to map the distribution of AIB3 protein by immunohistochemistry. Although AIB3 protein was detected in many tissues, the AIB3 immunoreactivities varied significantly from cell type to cell type. High levels of AIB3 immunoreactivity were observed in hormone target cells including the testicular Sertoli cells, follicular granulosa cells, and epithelial cells of the prostate, uterus, mammary gland, and kidney tubules. Medium and low levels of AIB3 immunoreactivities were also detected in a variety of other cell types. These results demonstrate that AIB3 mRNA and protein are preferentially expressed in specific cell types, suggesting that AIB3 may support the function of nuclear receptors in a cell type-specific manner.