RESUMO
Although deregulated expression of specific microRNAs (miRNAs) has been described in solid cancers and leukemias, little evidence of miRNA deregulation has been reported in ALK-positive (ALK(+)) anaplastic large cell lymphomas (ALCL). These tumors overexpress the major antiapoptotic protein myeloid cell leukemia 1 (MCL-1), a situation that could compensate for the lack of BCL-2. We report that ALK(+) ALCL cell lines and biopsy specimens (n = 20) express a low level of miR-29a and that this down-modulation requires an active NPM-ALK kinase. Murine models (transgenic mice and mouse embryonic fibroblast [MEF] cells), which allow conditional NPM-ALK fusion protein expression, showed an increase of miR-29a expression in the absence of NPM-ALK. Concordant results were observed after the abolition of NPM-ALK kinase activity (siALK or PF-2341066) in NPM-ALK(+) ALCL cell lines. In addition, we showed that low expression of miR-29a, probably through methylation repression, plays an important regulatory role in MCL-1 overexpression that could promote tumor cell survival by inhibiting apoptosis. Enforced miR-29a expression was found to modulate apoptosis through inhibition of MCL-1 expression in ALCL cell lines and in a xenografted model, with a concomitant tumor growth reduction. Thus, synthetic miR-29a represents a potential new tool to affect tumorigenesis in these lymphomas.
Assuntos
Apoptose/genética , Linfoma Anaplásico de Células Grandes/genética , MicroRNAs/genética , Proteínas Proto-Oncogênicas c-bcl-2/genética , Receptores Proteína Tirosina Quinases/genética , Quinase do Linfoma Anaplásico , Animais , Linhagem Celular Tumoral , Células Cultivadas , Regulação para Baixo/genética , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Linfoma Anaplásico de Células Grandes/metabolismo , Linfoma Anaplásico de Células Grandes/patologia , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Camundongos Transgênicos , MicroRNAs/metabolismo , MicroRNAs/fisiologia , Proteína de Sequência 1 de Leucemia de Células Mieloides , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Receptores Proteína Tirosina Quinases/metabolismo , Regulação para Cima/genética , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
We identified the first archaeal tRNA ribose 2'-O-methylase, aTrm56, belonging to the Cluster of Orthologous Groups (COG) 1303 that contains archaeal genes only. The corresponding protein exhibits a SPOUT S-adenosylmethionine (AdoMet)-dependent methyltransferase domain found in bacterial and yeast G18 tRNA 2'-O-methylases (SpoU, Trm3). We cloned the Pyrococcus abyssi PAB1040 gene belonging to this COG, expressed and purified the corresponding protein, and showed that in vitro, it specifically catalyzes the AdoMet-dependent 2'-O-ribose methylation of C at position 56 in tRNA transcripts. This tRNA methylation is present only in archaea, and the gene for this enzyme is present in all the archaeal genomes sequenced up to now, except in the crenarchaeon Pyrobaculum aerophilum. In this archaea, the C56 2'-O-methylation is provided by a C/D sRNP. Our work is the first demonstration that, within the same kingdom, two different mechanisms are used to modify the same nucleoside in tRNAs.