-
[show abstract]
[hide abstract]
ABSTRACT: The Ski-interacting protein SKIP/SNW1 functions as both a splicing factor and a transcriptional coactivator for induced genes. We showed previously that transcription elongation factors such as SKIP are dispensable in cells subjected to DNA damage stress. However, we report here that SKIP is critical for both basal and stress-induced expression of the cell cycle arrest factor p21(Cip1). RNAi chromatin immunoprecipitation (RNAi-ChIP) and RNA immunoprecipitation (RNA-IP) experiments indicate that SKIP is not required for transcription elongation of the gene under stress, but instead is critical for splicing and p21(Cip1) protein expression. SKIP interacts with the 3' splice site recognition factor U2AF65 and recruits it to the p21(Cip1) gene and mRNA. Remarkably, SKIP is not required for splicing or loading of U2AF65 at other investigated p53-induced targets, including the proapoptotic gene PUMA. Consequently, depletion of SKIP induces a rapid down-regulation of p21(Cip1) and predisposes cells to undergo p53-mediated apoptosis, which is greatly enhanced by chemotherapeutic DNA damage agents. ChIP experiments reveal that SKIP is recruited to the p21(Cip1), and not PUMA, gene promoters, indicating that p21(Cip1) gene-specific splicing is predominantly cotranscriptional. The SKIP-associated factors DHX8 and Prp19 are also selectively required for p21(Cip1) expression under stress. Together, these studies define a new step that controls cancer cell apoptosis.
Genes & development 04/2011; 25(7):701-16. · 12.08 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The transcriptional factor Sox2 and epidermal growth factor receptor (Egfr)-mediated signaling are both required for self-renewal of neural precursor cells (NPCs). However, the mechanism by which these factors coordinately regulate this process is largely unknown. Here we show that Egfr-mediated signaling promotes Sox2 expression, which in turn binds to the Egfr promoter and directly upregulates Egfr expression. Knockdown of Sox2 by RNA interference downregulates Egfr expression and attenuates colony formation of NPCs, whereas overexpression of Sox2 elevates Egfr expression and promotes NPC self-renewal. Moreover, the effect of Sox2 on NPC self-renewal is completely inhibited by AG1478, a specific inhibitor for Egfr; it is also inhibited by LY294002 and U0126, selective antagonists for phosphatidylinositol 3-kinase (PI3K) and extracellular signal-regulated kinase (Erk1/2), respectively. Collectively, we conclude that NPC self-renewal is enhanced through a novel cellular feedback loop with mutual regulation of Egfr and Sox2.
Stem Cells 10/2009; 28(2):279-86. · 7.78 Impact Factor
-
Yupeng Chen,
Lei Shi, Lirong Zhang,
Ruifang Li,
Jing Liang,
Wenhua Yu,
Luyang Sun,
Xiaohan Yang,
Yan Wang,
Yu Zhang,
Yongfeng Shang
[show abstract]
[hide abstract]
ABSTRACT: SOX genes encode a family of high-mobility group transcription factors that play critical roles in organogenesis. The functional specificity of different SOX proteins and the tissue specificity of a particular SOX factor are largely determined by the differential partnership of SOX transcription factors with other transcription regulators, many of which have not yet been discovered. Virtually all members of the SOX family have been found to be deregulated in a wide variety of tumors. However, little is known about the cellular and molecular behaviors involved in the oncogenic potential of SOX proteins. Using cell culture experiments, tissue analysis, molecular profiling, and animal studies, we report here that SOX2 promotes cell proliferation and tumorigenesis by facilitating the G(1)/S transition and through its transcription regulation of the CCND1 gene in breast cancer cells. In addition, we identified beta-catenin as the transcription partner for SOX2 and demonstrated that SOX2 and beta-catenin act in synergy in the transcription regulation of CCND1 in breast cancer cells. Our experiments not only determined a role for SOX2 in mammary tumorigenesis but also revealed another activity of the multifunctional protein, beta-catenin.
Journal of Biological Chemistry 07/2008; 283(26):17969-78. · 4.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Pax6 is a key regulator in the neuronal fate determination as well as the proliferation of neural stem cells, but the mechanisms are still unknown. Our study shows that Pax6 regulate the proliferation of neural progenitor cells of cortical subventricular zone, through direct modulation of the Sox2 expression during the late developmental stage in mice. We found a dramatic decrease in the number of Sox2+ neural progenitor cells in the subventricular zone of E18.5 Pax6(-/-) mice. We confirmed that Pax6 could bind to the Sox2 promoter by chromatin immunoprecipitation assay and activate Sox2 expression by a luciferase reporter gene assay. Moreover, neural progenitors isolated from the Pax6(-/-) embryos showed a decreased neurosphere formation as well as proliferation.
Neuroreport 04/2008; 19(4):413-7. · 1.66 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The PAX6 gene mutation in aniridia has been studied in various ethnic patients, but not well studied in the Chinese population. In the present study, we have investigated the PAX6 gene mutation in a Chinese family with congenital aniridia.
Total genomic DNA was isolated from peripheral blood of three aniridia patients (who also suffered from bilateral congenital cataracts) and two non-carriers in a Chinese family. Fourteen exons of the PAX6 gene were amplified by polymerase chain reaction (PCR). PCR products of each exon were analyzed by single strand conformational polymorphism (SSCP). The PCR products with abnormal SSCP patterns were subcloned and sequenced to identify the mutation.
Abnormal SSCP patterns were found in all affected patients but not in non-carrier family members. A novel mutation (c.857delG) in exon 7 was detected by sequencing analysis. This frame shift mutation was predicted to lead to a pre-stop codon in exon 8, and generate a novel 40 amino acid peptide from codon 165.
A novel PAX6 gene mutation was identified in a Chinese aniridia family. This mutation may also contribute to congenital cataracts in these aniridia patients.
Molecular vision 02/2005; 11:335-7. · 2.20 Impact Factor
