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2.
Nature ; 627(8002): 212-220, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38355801

RESUMO

Circular RNAs (circRNAs), which are increasingly being implicated in a variety of functions in normal and cancerous cells1-5, are formed by back-splicing of precursor mRNAs in the nucleus6-10. circRNAs are predominantly localized in the cytoplasm, indicating that they must be exported from the nucleus. Here we identify a pathway that is specific for the nuclear export of circular RNA. This pathway requires Ran-GTP, exportin-2 and IGF2BP1. Enhancing the nuclear Ran-GTP gradient by depletion or chemical inhibition of the major protein exporter CRM1 selectively increases the nuclear export of circRNAs, while reducing the nuclear Ran-GTP gradient selectively blocks circRNA export. Depletion or knockout of exportin-2 specifically inhibits nuclear export of circRNA. Analysis of nuclear circRNA-binding proteins reveals that interaction between IGF2BP1 and circRNA is enhanced by Ran-GTP. The formation of circRNA export complexes in the nucleus is promoted by Ran-GTP through its interactions with exportin-2, circRNA and IGF2BP1. Our findings demonstrate that adaptors such as IGF2BP1 that bind directly to circular RNAs recruit Ran-GTP and exportin-2 to export circRNAs in a mechanism that is analogous to protein export, rather than mRNA export.


Assuntos
Transporte Ativo do Núcleo Celular , Núcleo Celular , Transporte de RNA , RNA Circular , Transporte Ativo do Núcleo Celular/fisiologia , Núcleo Celular/metabolismo , Guanosina Trifosfato/metabolismo , Carioferinas/antagonistas & inibidores , Carioferinas/deficiência , Carioferinas/genética , Carioferinas/metabolismo , Proteínas Nucleares/metabolismo , Proteína ran de Ligação ao GTP/metabolismo , RNA Circular/metabolismo , Precursores de RNA/genética , Precursores de RNA/metabolismo , Proteínas de Ligação a RNA/metabolismo , Proteína Exportina 1/metabolismo , Transporte Proteico
3.
RNA ; 27(4): 411-419, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33479117

RESUMO

Ribosomes are the macromolecular machines at the heart of protein synthesis; however, their function can be modulated by a variety of additional protein factors that directly interact with them. Here, we report the cryo-EM structure of human Ebp1 (p48 isoform) bound to the human 80S ribosome at 3.3 Å resolution. Ebp1 binds in the vicinity of the peptide exit tunnel on the 80S ribosome, and this binding is enhanced upon puromycin-mediated translational inhibition. The association of Ebp1 with the 80S ribosome centers around its interaction with ribosomal proteins eL19 and uL23 and the 28S rRNA. Further analysis of the Ebp1-ribosome complex suggests that Ebp1 can rotate around its insert domain, which may enable it to assume a wide range of conformations while maintaining its interaction with the ribosome. Structurally, Ebp1 shares homology with the methionine aminopeptidase 2 family of enzymes; therefore, this inherent flexibility may also be conserved.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/química , Biossíntese de Proteínas , RNA Ribossômico/química , Proteínas de Ligação a RNA/química , Proteínas Ribossômicas/química , Ribossomos/química , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Sítios de Ligação , Microscopia Crioeletrônica , Humanos , Modelos Moleculares , Ligação Proteica , Biossíntese de Proteínas/efeitos dos fármacos , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Inibidores da Síntese de Proteínas/farmacologia , Puromicina/farmacologia , RNA Ribossômico/genética , RNA Ribossômico/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Proteínas Ribossômicas/genética , Proteínas Ribossômicas/metabolismo , Ribossomos/genética , Ribossomos/metabolismo , Termodinâmica
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