RESUMO
HnRNPs are ubiquitously expressed RNA-binding proteins, tightly controlling posttranscriptional gene regulation. Consequently, hnRNP networks are essential for cellular homeostasis and their dysregulation is associated with cancer and other diseases. However, the physiological function of hnRNPs in non-cancerous cell systems are poorly understood. We analyzed the importance of HNRNPDL in endothelial cell functions. Knockdown of HNRNPDL led to impaired proliferation, migration and sprouting of spheroids. Transcriptome analysis identified cyclin D1 (CCND1) and tropomyosin 4 (TPM4) as targets of HNRNPDL, reflecting the phenotypic changes after knockdown. Our findings underline the importance of HNRNPDL for the homeostasis of physiological processes in endothelial cells.
Assuntos
Células Endoteliais , Ribonucleoproteínas Nucleares Heterogêneas , Ribonucleoproteínas Nucleares Heterogêneas/genética , Células Endoteliais/metabolismo , Proteínas de Ligação a RNA/metabolismoRESUMO
HnRNP D, better known as AUF1, is an extensively studied protein that controls a variety of cellular pathways. Consequently, its expression has to be tightly regulated to prevent the onset of pathologies. In contrast, the cellular functions and regulation of its ubiquitously expressed paralog hnRNP DL are barely explored. Here, we present an intricate crosstalk between these two proteins. Both hnRNP D and DL are able to control their own expression by alternative splicing of cassette exons in their 3'UTRs. Exon inclusion produces mRNAs degraded by nonsense-mediated decay. Moreover, hnRNP D and DL control the expression of one another by the same mechanism. Thus, we identified two novel ways of how hnRNP D expression is controlled. The tight interconnection of expression control directly links hnRNP DL to hnRNP D-related diseases and emphasizes the importance of a systematic analysis of its cellular functions.
Assuntos
Processamento Alternativo , Regulação da Expressão Gênica/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo D/genética , Ribonucleoproteínas Nucleares Heterogêneas/genética , Degradação do RNAm Mediada por Códon sem Sentido/genética , Ribonucleoproteínas/genética , Regiões 3' não Traduzidas/genética , Éxons , Genes Reporter , Células HeLa , Ribonucleoproteína Nuclear Heterogênea D0 , Ribonucleoproteínas Nucleares Heterogêneas Grupo D/fisiologia , Ribonucleoproteínas Nucleares Heterogêneas Grupo L/genética , Homeostase , Humanos , RNA Mensageiro/genética , Ribonucleoproteínas/fisiologiaRESUMO
The MYC-MAX-MXD network is involved in the regulation of cell differentiation and proliferation. Hypoxia affects the expression levels of several members of this network, but changes specific to MAX expression have so far not been shown. We found that in endothelial cells, hypoxia induces alternative splicing of MAX, thereby increasing the expression of two MAX isoforms that differ from the wild type in their 3' end. Isoform C is degraded by nonsense-mediated decay and isoform E encodes a highly unstable protein. The instability of isoform E is conferred by 36 isoform-specific amino acids, which have the capacity to destabilize heterologous proteins. Both splicing events are therefore unproductive and serve the purpose to downregulate the wild type protein.
