Project description:To further investigate the underlying function and molecular mechanism of FBL in DNA damage response, we conducted RNA sequencing analysis (RNA-seq) and detected the genome-wide transcriptomic changes in HCT116 cells and shFBL-HCT116 cells following MMC treatment. Together, these data indicate that the activation of the FBL/YBX1 signaling axis upon DNA damage regulates the transcriptional activation of genes directly involved in the repair of DNA DSBs, such as BRCA1 and contributes to promoting the resistance of cells to DNA-damaging agents.
Project description:In order to study the molecular mechanism of FBL in cells, this project constructed the full length of FBL into the SFB (S-Flag-SBP tag) vector, and constructed a stable cell line overexpressing FBL. Affinity chromatography combined with LC-MS/MS technology to screen FBL interacting proteins.
Project description:Breast cancer is the second leading cause of death in women worldwide, with triple-negative breast cancer (TNBC) having the worst prognosis. Although there are numerous studies on TNBC, there is no effective treatment for it, and it is still a major problem today. Studies on PIWI-interacting RNAs (piRNAs) are increasing and investigating the mechanism of piRNAs in the proliferation and metastasis of TNBC may lead to new potential treatment targets. Here, we identified a novel piRNA, piR-YBX1, which was downregulated in TNBC compared to matched normal breast tissue. Overexpression of piR-YBX1 significantly inhibited the proliferation, migration, invasion ability of TNBC cells both in vivo and in vitro. Mechanistically, piR-YBX1 could bind directly to mRNA of YBX1 and overexpression of piR-YBX1 downregulated YBX1 in both mRNA and protein levels, while the function of piR-YBX1 could be partly rescued by overexpression of YBX1. In addition, YBX1 could bind to RAF1 which is the key molecule in the MAPK signaling pathway, and overexpression of piR-YBX1 inhibited the p-MEK and p-ERK1/2 which can be reverted by YBX1. In conclusion, our findings discovered that the piR-YBX1/YBX1/MAPK axis suppresses the proliferation and metastasis of TNBC and therefore piR-YBX1 has the potential to be an effective therapeutic agent for breast cancer.
Project description:In order to identify YBX1 binding sites on endogenous RNA, we performed HITS-CLIP on endogenous YBX1 We used a previously published method to perform HITS-CLIP on endogenous YBX1 (Licatalosi D, et al. 2008, Nature 456:464-U22)
Project description:Pluripotent stem cells have been shown to have unique nuclear properties, e.g., hyperdynamic chromatin and large, condensed nucleoli. However, the contribution of the latter unique nucleolar character to pluripotency has not been well understood. Here, we show fibrillarin (FBL), a critical methyltransferase for ribosomal RNA (rRNA) processing in nucleoli, as one of the proteins highly expressed in pluripotent embryonic stem (ES) cells. Stable expression of FBL in ES cells prolonged the pluripotent state of mouse ES cells cultured in the absence of leukemia inhibitory factor (LIF). Analyses using deletion mutants and a point mutant revealed that the methyltransferase activity of FBL regulates stem cell pluripotency. Knock down of this gene led to significant delays in rRNA processing, growth inhibition, and apoptosis in mouse ES cells. Interestingly, both partial knock down of FBL and treatment with actinomycin D, an inhibitor for rRNA synthesis, induced the expression of differentiation markers in the presence of LIF and promoted stem cell differentiation into neuronal lineages. Moreover, we identified p53 signaling as the regulatory pathway for pluripotency and differentiation of ES cells. These results suggest that proper activity of rRNA production in nucleoli is a novel factor for the regulation of pluripotency and differentiation ability of ES cells. Tc-inducible FBL-knock down ES cells were cultured for 2 days with or without Tc in the presence of LIF. These 2 conditions were analysed transcription profile.
Project description:In order to identify YBX1 binding sites on tRNA fragments, we performed small-RNA HITS-CLIP on endogenous YBX1 We used a previously published method to perform HITS-CLIP on endogenous YBX1 (Chi SW, et al. 2009, Nature 460:479)
Project description:YBX1 is a multifunctional protein involved in the control of transcription and translation. We identified YBX1 as an target of MEK/ERK signaling in colorectal cancer cell lines. We performed a ChIP-chip analysis of HCT116 cells to identify new potential target genes of YBX1. Comparison of input DNA fragments with fragments coprecipitated with YBX1 in HCT116 cells.
Project description:In order to identify YBX1-dependent targets that are modulated under hypoxic conditions, we used control and YBX1 knockdown cells grown under normoxia and hypoxia to profile gene expression levels. Control and YBX1-knockdown cells were grown and profiled under hypoxia and normoxia to identify YBX1-dependent hypoxia-induced target transcripts.
Project description:Fibrillarin (FBL) is a highly conserved nucleolar methyltransferase responsible for methylation of ribosomal RNA and proteins. Here we reveal a role for FBL in DNA damage response and its impact on cancer proliferation and sensitivity to DNA damaging agents. FBL is highly expressed in various cancers and correlates with poor survival outcomes in cancer patients. Knockdown of FBL sensitizes tumor cells and xenografts to DNA crosslinking agents, and leads to HR-mediated DNA repair defects. We identify Y-box binding protein-1 (YBX1) as a key interacting partner of FBL, and FBL increases the nuclear accumulation of YBX1 in response to DNA damage. We show that FBL promotes the expression of BRCA1 by increasing the binding of YBX1 to the BRCA1 promoter. Our study sheds light on the regulatory mechanism of FBL in tumorigenesis and DNA damage response, providing potential therapeutic targets to overcome chemoresistance in cancer.