RESUMO
Translocations or mutations of FUS, EWSR1, and TAF15 (FET) result in distinct genetic diseases. N-terminal translocations of any FET protein to a series of transcription factors yields chimeric proteins that contribute to sarcomagenesis, whereas mutations in the conserved COOH-terminal domain of wild-type FUS were recently shown to cause familial amyotrophic lateral sclerosis. We thus investigated whether the loss of one FUS allele by translocation in liposarcoma may be followed by mutations in either the remaining FUS allele or the paralogous EWSR1. Furthermore, we investigated the strength of the FET promoters and their contributions to sarcomagenesis given the proteins' frequent involvement in oncogenic translocations. We sequenced the respective genomic regions of both FUS and EWSR1 in 96 liposarcoma samples. Additionally, we determined FET transcript and protein levels in several liposarcoma cell lines. We did not observe sequence variations in either FUS or EWSR1. However, protein copy numbers reached an impressive 0.9 and 5.5 Mio of FUS and EWSR1 per tumor cell, respectively. Compared with adipose-derived stem cells, FUS and EWSR1 protein expression levels were elevated on average 28.6-fold and 7.3-fold, respectively. TAF15 mRNA levels were elevated on average 3.9-fold, although with a larger variation between samples. Interestingly, elevated TAF15 mRNA levels did not translate to strongly elevated protein levels, consistent with its infrequent occurrence as translocation partner in tumors. These results suggest that the powerful promoters of FET genes are predominantly responsible for the oncogenic effect of transcription factor translocations in sarcomas.
Assuntos
Proteínas de Ligação a Calmodulina/genética , Lipossarcoma/genética , RNA Mensageiro/genética , Proteína FUS de Ligação a RNA/genética , Proteínas de Ligação a RNA/genética , Fatores Associados à Proteína de Ligação a TATA/genética , Alelos , Animais , Sequência de Bases , Proteínas de Ligação a Calmodulina/biossíntese , Linhagem Celular Transformada , Linhagem Celular Tumoral , Éxons , Células HEK293 , Humanos , Lipossarcoma/metabolismo , Regiões Promotoras Genéticas , RNA Mensageiro/biossíntese , Proteína EWS de Ligação a RNA , Proteína FUS de Ligação a RNA/biossíntese , Proteínas de Ligação a RNA/biossíntese , Spodoptera/genética , Spodoptera/metabolismo , Fatores Associados à Proteína de Ligação a TATA/biossíntese , Transfecção , Translocação Genética , Regulação para CimaRESUMO
Mature microRNAs (miRNAs) are single-stranded RNA molecules of 20-23 nucleotide (nt) length that control gene expression in many cellular processes. These molecules typically reduce the stability of mRNAs, including those of genes that mediate processes in tumorigenesis, such as inflammation, cell cycle regulation, stress response, differentiation, apoptosis and invasion. miRNA targeting is mostly achieved through specific base-pairing interactions between the 5' end ('seed' region) of the miRNA and sites within coding and untranslated regions (UTRs) of mRNAs; target sites in the 3' UTR lead to more effective mRNA destabilization. Since miRNAs frequently target hundreds of mRNAs, miRNA regulatory pathways are complex. To provide a critical overview of miRNA dysregulation in cancer, we first discuss the methods currently available for studying the role of miRNAs in cancer and then review miRNA genomic organization, biogenesis and mechanism of target recognition, examining how these processes are altered in tumorigenesis. Given the critical role miRNAs play in tumorigenesis processes and their disease-specific expression, they hold potential as therapeutic targets and novel biomarkers.
