IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Smaug1-silencing foci formation depends on RNA binding and conserved protein domains and requires the PB components Hedls and RCK/p54.
Autor/es:
HABIF, MARTIN; BOCCACCIO, GRACIELA L.
Lugar:
Bariloche, Rio Negro,Argentina
Reunión:
Congreso; Gene Expression and RNA processing; 2007
Resumen:
Smaug1-silencing foci formation depends on RNA binding and conserved protein domains and requires the PB components Hedls and RCK/p54. Martín Habif and Graciela Lidia Boccaccio (Instituto Leloir - FCEyN, Universidad de Buenos Aires, Buenos Aires - Argentina). Stress Granules (SG) and Processing Bodies (PB) are related cytoplasmic mRNA-silencing foci. While SG are transiently induced during the stress response and contains abortive translation initiation complexes, PB are constitutive and contains mostly de-adenylated mRNAs. PB include molecules involved in mRNA decay as well as RNA binding proteins that mediates translational repression. We have previously shown that mammalian Smaug1 forms cytoplasmic foci and translationally represses transcripts carrying a specific RNA motif, the Smaug Recognition Element (SRE) (Baez and Boccaccio, JBC 2005). Here we demostrate that 82% of hSmaug1-ECFP foci colocalized with the decapping activator and PB marker Dcp1a. Colocalization with other PB markers Xrn1 and Hedls was also observed. Moreover, the presence of PB was enhanced in hSmaug1-tranfected cells. In addition 18% of hSmaug1-ECFP foci also contained the stress granule marker TIA-1, known to be mildly recruited to PB. siRNA-mediated gene silencing of the PB components Hedls/Ge-1 or RCK/p54/Me31B/DDX6, known to be required for PB integrity, resulted in marked decrease of hSmaug1 foci formation. Thus, hSmaug1 foci are PB-related structures where translational repression of a pool of SRE-containing transcripts might take place. By using hSmaug1 deletion mutants, we found that both the RNA binding domain (SAM) and a region in the N-terminus of unknown function, that is highly conserved among Smaug homologues (Smaug Similarity Regions), are required to target the molecule to PB. Furthermore, neither isolated SAM nor the SSR regions were able to localize to PB when expressed separately. Constructions lacking the N-terminal region of hSmaug1 resulted in almost the complete lost of endogenous PB when overexpressed, suggesting the titration of one or more PB components by the C-terminal part of the molecule. We are currently investigating the relevance of PB components and of hSmaug1 domains in hSmaug1-mediated translational repression. Supported by NIH (USA), University of Buenos Aires, CONICET and ANPCyT, (Argentina).