RESUMEN
Heterogeneous nuclear ribonucleoproteins (hnRNPs), a family of RNA-binding proteins, play important roles in various biological processes. However, the roles of hnRNPs members in immunity and inflammation remain to be fully understood. By a functional screening for hnRNPs members in LPS-stimulated macrophage inflammatory response, we identified hnRNP UL1 as a negative regulator of NF-κB-mediated inflammation. hnRNP UL1 constrains NF-κB-triggered transcriptional expression of pro-inflammatory cytokines in response to innate stimuli. Perturbation of hnRNP UL1 enhanced pro-inflammatory cytokine production in macrophages. In vivo deficiency of hnRNP UL1 increased the pro-inflammatory cytokine production once challenged with LPS. Accordingly, the expression of hnRNP UL1 decreased in peripheral blood mononuclear cells of rheumatoid arthritis patients. Mechanistically, hnRNP UL1 competes with NF-κB to bind κB sites to constrain the magnitude and duration of inflammatory response. Meanwhile, the broadly and dynamically binding of hnRNP UL1 on the target genes' promoter during inflammatory response is unraveled. Our study adds new insight into the functions of hnRNPs in NF-κB-mediated inflammation, proposing a potential therapeutic strategy for controlling inflammatory autoimmune diseases.
Asunto(s)
Ribonucleoproteínas Nucleares Heterogéneas , FN-kappa B , Proteínas Nucleares , Factores de Transcripción , Citocinas/metabolismo , Ribonucleoproteínas Nucleares Heterogéneas/metabolismo , Humanos , Inflamación/genética , Leucocitos Mononucleares/metabolismo , Lipopolisacáridos , FN-kappa B/metabolismo , Proteínas Nucleares/metabolismo , Proteínas de Unión al ARN/genética , Factores de Transcripción/metabolismoRESUMEN
hnRNP UL1 plays an important role in cell nuclei, where it is recruited to DNA damage sites and is involved in the repair of DNA double-strand breaks. Furthermore, this protein is known as a transcriptional repressor of RNA polymerase II genes. In the present study, we have shown that hnRNP UL1 is also localized in the nucleoli of human cells. Upon investigating its function, we found that hnRNP UL1 stimulates ribosomal DNA (rDNA) gene transcription. Moreover, we observed that cells with hnRNP UL1 silencing exhibited increased sensitivity to DNA damage. We also showed that hnRNP UL1 interacts with γH2A.X, RPA32, XRCC1, and Chk1 in cell nucleoli, suggesting its involvement in the repair of rDNA damage.
Asunto(s)
Nucléolo Celular , Reparación del ADN , Ribonucleoproteínas Nucleares Heterogéneas , Proteínas Nucleares , Factores de Transcripción , Nucléolo Celular/genética , Roturas del ADN de Doble Cadena , ADN Ribosómico/genética , Ribonucleoproteínas Nucleares Heterogéneas/genética , Humanos , Proteínas Nucleares/genética , Factores de Transcripción/genética , Transcripción Genética , Proteína 1 de Reparación por Escisión del Grupo de Complementación Cruzada de las Lesiones por Rayos X/genéticaRESUMEN
BACKGROUND: Somatic cell reprogramming is the process that allows differentiated cells to revert to a pluripotent state. In contrast to the extensively studied rewiring of epigenetic and transcriptional programs required for reprogramming, the dynamics of post-transcriptional changes and their associated regulatory mechanisms remain poorly understood. Here we study the dynamics of alternative splicing changes occurring during efficient reprogramming of mouse B cells into induced pluripotent stem (iPS) cells and compare them to those occurring during reprogramming of mouse embryonic fibroblasts. RESULTS: We observe a significant overlap between alternative splicing changes detected in the two reprogramming systems, which are generally uncoupled from changes in transcriptional levels. Correlation between gene expression of potential regulators and specific clusters of alternative splicing changes enables the identification and subsequent validation of CPSF3 and hnRNP UL1 as facilitators, and TIA1 as repressor of mouse embryonic fibroblasts reprogramming. We further find that these RNA-binding proteins control partially overlapping programs of splicing regulation, involving genes relevant for developmental and morphogenetic processes. CONCLUSIONS: Our results reveal common programs of splicing regulation during reprogramming of different cell types and identify three novel regulators of this process and their targets.