RESUMO
Import-Karyopherin or Importin proteins bind nuclear localization signals (NLSs) to mediate the import of proteins into the cell nucleus. Karyopherin ß2 or Kapß2, also known as Transportin, is a member of this transporter family responsible for the import of numerous RNA binding proteins. Kapß2 recognizes a targeting signal termed the PY-NLS that lies within its cargos to target them through the nuclear pore complex. The recognition of PY-NLS by Kapß2 is conserved throughout eukaryotes. Kap104, the Kapß2 homolog in Saccharomyces cerevisiae, recognizes PY-NLSs in cargos Nab2, Hrp1, and Tfg2. We have determined the crystal structure of Kapß2 bound to the PY-NLS of the mRNA processing protein Nab2 at 3.05-Å resolution. A seven-residue segment of the PY-NLS of Nab2 is observed to bind Kapß2 in an extended conformation and occupies the same PY-NLS binding site observed in other Kapß2·PY-NLS structures.
Assuntos
Sinais de Localização Nuclear/química , Proteínas de Transporte Nucleocitoplasmático/química , Proteínas de Ligação a RNA/química , Proteínas de Saccharomyces cerevisiae/química , Saccharomyces cerevisiae/metabolismo , beta Carioferinas/química , Sequência de Aminoácidos , Sítios de Ligação , Núcleo Celular/metabolismo , Cristalografia por Raios X , Humanos , Interações Hidrofóbicas e Hidrofílicas , Dados de Sequência Molecular , Sinais de Localização Nuclear/metabolismo , Proteínas de Transporte Nucleocitoplasmático/metabolismo , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , beta Carioferinas/metabolismoRESUMO
Lysine acetylation regulates gene expression through modulating protein-protein interactions in chromatin. Chemical inhibition of acetyl-lysine binding bromodomains of the major chromatin regulators BET (bromodomain and extraterminal domain) proteins has been shown to effectively block cell proliferation in cancer and inflammation. However, whether selective inhibition of individual BET bromodomains has distinctive functional consequences remains only partially understood. In this study, we show that selective chemical inhibition of the first bromodomain of BET proteins using our small-molecule inhibitor, Olinone, accelerated the progression of mouse primary oligodendrocyte progenitors toward differentiation, whereas inhibition of both bromodomains of BET proteins hindered differentiation. This effect was target specific, as it was not detected in cells treated with inactive analogs and independent of any effect on proliferation. Therefore, selective chemical modulation of individual bromodomains, rather than use of broad-based inhibitors, may enhance regenerative strategies in disorders characterized by myelin loss such as aging and neurodegeneration.