RESUMO
Dysregulated splicing is a common event in cancer even in the absence of mutations in the core splicing machinery. The aberrant long non-coding transcriptome constitutes an uncharacterized level of regulation of post-transcriptional events in cancer. Here, we found that the stress-induced long non-coding RNA (lncRNA), LINC02657 or LASTR (lncRNA associated with SART3 regulation of splicing), is upregulated in hypoxic breast cancer and is essential for the growth of LASTR-positive triple-negative breast tumors. LASTR is upregulated in several types of epithelial cancers due to the activation of the stress-induced JNK/c-JUN pathway. Using a mass-spectrometry based approach, we identified the RNA-splicing factor SART3 as a LASTR-interacting partner. We found that LASTR promotes splicing efficiency by controlling SART3 association with the U4 and U6 small nuclear ribonucleoproteins (snRNP) during spliceosome recycling. Intron retention induced by LASTR depletion downregulates expression of essential genes, ultimately decreasing the fitness of cancer cells.
Assuntos
Antígenos de Neoplasias/metabolismo , Neoplasias/genética , RNA Longo não Codificante/metabolismo , Proteínas de Ligação a RNA/metabolismo , Ribonucleoproteína Nuclear Pequena U4-U6/metabolismo , Estresse Fisiológico , Animais , Hipóxia Celular , Linhagem Celular Tumoral , Células Epiteliais/metabolismo , Células Epiteliais/patologia , Regulação Neoplásica da Expressão Gênica , Genes Essenciais , Humanos , Íntrons/genética , Sistema de Sinalização das MAP Quinases , Camundongos Nus , Splicing de RNA/genética , RNA Longo não Codificante/genética , Regulação para Cima/genéticaRESUMO
Loss of chromosome 9p21 is observed in one-thirds of clear-cell renal cell carcinoma (ccRCC) and is associated with poorer patient survival. Unexpectedly, 9p21 LOH does not lead to decreased expression of the 9p21 tumor suppressor genes, CDKN2A and CDKN2B, suggesting alternative mechanisms of 9p-mediated tumorigenesis. Concordantly, CRISPR-mediated 9p21 deletion promotes growth of immortalized human embryonic kidney epithelial cells independently of the CDKN2A/B pathway inactivation. The 9p21 locus has a highly accessible chromatin structure, suggesting that 9p21 loss might contribute to kidney cancer progression by dysregulating genes distal to the 9p21 locus. We identified several 9p21 regulatory hubs by assessing which of the 9p21-interacting genes are dysregulated in 9p21-deleted kidney cells and ccRCCs. By focusing on the analysis of the homeobox gene 13 (HOXB13) locus, we found that 9p21 loss relieves the HOXB13 locus, decreasing HOXB13 methylation and promoting its expression. Upregulation of HOXB13 facilitates cell growth and is associated with poorer survival of patients with ccRCC. IMPLICATIONS: The results of our study propose a novel tumor suppressive mechanism on the basis of coordinated expression of physically associated genes, providing a better understanding of the role of chromosomal deletions in cancer.
Assuntos
Carcinoma de Células Renais/genética , Deleção Cromossômica , Cromossomos Humanos Par 9/genética , Proteínas de Homeodomínio/genética , Neoplasias Renais/genética , Regulação para Cima , Carcinoma de Células Renais/metabolismo , Carcinoma de Células Renais/patologia , Sequenciamento de Cromatina por Imunoprecipitação/métodos , Inibidor de Quinase Dependente de Ciclina p15/genética , Inibidor p16 de Quinase Dependente de Ciclina/genética , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Deleção de Genes , Regulação Neoplásica da Expressão Gênica , Células HEK293 , Proteínas de Homeodomínio/metabolismo , Humanos , Estimativa de Kaplan-Meier , Neoplasias Renais/metabolismo , Neoplasias Renais/patologia , Perda de Heterozigosidade , RNA Longo não Codificante/genética , RNA-Seq/métodosRESUMO
The Tet 5-methylcytosine dioxygenases catalyze DNA demethylation by producing 5-hydroxymethylcytosine and further oxidized products. Tet1 and Tet2 are highly expressed in mouse pluripotent cells and downregulated to different extents in somatic cells, but the transcriptional mechanisms are unclear. Here we defined the promoter and enhancer domains in Tet1 and Tet2. Within a 15-kb "superenhancer" of Tet1, there are two transcription start sites (TSSs) with different activation patterns during development. A 6-kb promoter region upstream of the distal TSS is highly active in naive pluripotent cells, autonomously reports Tet1 expression in a transgenic system, and rapidly undergoes DNA methylation and silencing upon differentiation in cultured cells and native epiblast. A second TSS downstream, associated with a constitutively weak CpG-rich promoter, is activated by a neighboring enhancer in naive embryonic stem cells (ESCs) and primed epiblast-like cells (EpiLCs). Tet2 has a CpG island promoter with pluripotency-independent activity and an ESC-specific distal intragenic enhancer; the latter is rapidly downregulated in EpiLCs. Our study reveals distinct modes of transcriptional regulation at Tet1 and Tet2 during cell state transitions of early development. New transgenic reporters using Tet1 and Tet2 cis-regulatory domains may serve to distinguish nuanced changes in pluripotent states and the underlying epigenetic variations.