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Dendritic BC1 RNA in translational control mechanisms.

Wang H, Iacoangeli A, Lin D, Williams K, Denman RB, Hellen CU, Tiedge H - J. Cell Biol. (2005)

Bottom Line: We report that small untranslated BC1 RNA is a specific effector of translational control both in vitro and in vivo.A translational repression element is contained within the unique 3' domain of BC1 RNA.Thus, BC1 RNA modulates translation-dependent processes in neurons and germs cells by directly interacting with translation initiation factors.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Pharmacology, State University of New York, Health Science Center at Brooklyn, Brooklyn, NY 11203, USA.

ABSTRACT
Translational control at the synapse is thought to be a key determinant of neuronal plasticity. How is such control implemented? We report that small untranslated BC1 RNA is a specific effector of translational control both in vitro and in vivo. BC1 RNA, expressed in neurons and germ cells, inhibits a rate-limiting step in the assembly of translation initiation complexes. A translational repression element is contained within the unique 3' domain of BC1 RNA. Interactions of this domain with eukaryotic initiation factor 4A and poly(A) binding protein mediate repression, indicating that the 3' BC1 domain targets a functional interaction between these factors. In contrast, interactions of BC1 RNA with the fragile X mental retardation protein could not be documented. Thus, BC1 RNA modulates translation-dependent processes in neurons and germs cells by directly interacting with translation initiation factors.

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Translation in X. laevis oocytes, repressed by the 3′ BC1 domain, is restored by joint replenishment with eIF4A and PABP. Luciferase mRNA (Luc) was coinjected into stage VI oocytes with ∼400 nM 3′ BC1 domain, 100 nM eIF4A, and/or 100 nM PABP. Luminescence was measured after 1 h. Only replenishment with eIF4A and PABP in combination restored 3′ BC1–repressed translation to a level that was statistically indistinguishable from unrepressed translation. Quantitative analysis of four experiments is shown (one-way ANOVA, Scheffe's multiple comparison post hoc analysis, ***, P < 0.001). The observed differences among 3′ BC1, 3′ BC1 + eIF4A, and 3′ BC1 + PABP were not statistically significant.
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fig3: Translation in X. laevis oocytes, repressed by the 3′ BC1 domain, is restored by joint replenishment with eIF4A and PABP. Luciferase mRNA (Luc) was coinjected into stage VI oocytes with ∼400 nM 3′ BC1 domain, 100 nM eIF4A, and/or 100 nM PABP. Luminescence was measured after 1 h. Only replenishment with eIF4A and PABP in combination restored 3′ BC1–repressed translation to a level that was statistically indistinguishable from unrepressed translation. Quantitative analysis of four experiments is shown (one-way ANOVA, Scheffe's multiple comparison post hoc analysis, ***, P < 0.001). The observed differences among 3′ BC1, 3′ BC1 + eIF4A, and 3′ BC1 + PABP were not statistically significant.

Mentions: We used the X. laevis oocyte system for these experiments. Recombinant eIF4A and PABP were coinjected with the 3′ BC1 domain either individually or in combination (Fig. 3). Luciferase activity was used as an index for relative translational efficiency; this efficiency was significantly reduced in the presence of the 3′ BC1 domain. Supplementation with eIF4A or PABP alone resulted in a moderate recovery of translation; however, this recovery failed to reach statistical significance (Fig. 3). In contrast, 3′ BC1–mediated repression could be overcome by concurrent titration with eIF4A and PABP in stoichiometric ratio (Fig. 3). At 100 nM of both factors, translational efficiency was restored to 87% of nonrepressed levels. (We presume that some of the injected RNA is chaperoned in living cells, i.e., is not functionally available, thus resulting in a lower requirement for rescue proteins relative to repressor.) Higher concentrations of eIF4A and PABP resulted in overtitration, i.e., failure to restore translational efficiency (Kahvejian et al., 2005). eIF4A and PABP are expressed at rather low levels in stage VI X. laevis oocytes, unlike ribosomes, eIF4G, ePAB, and other factors that are more abundant (Audet et al., 1987; Zelus et al., 1989; Stambuk and Moon, 1992; Keiper and Rhoads, 1999; Voeltz et al., 2001). Although it remains to be established whether the same two factors are also limiting at the synapse, similarities in translational control mechanisms have been noted between oocytes and neuronal microdomains (Richter, 2000). On the other hand, the target of translational repression does not necessarily have to be limiting as long as the local concentration of the repressor is sufficiently high, as is the case with BC1 RNA (Chicurel et al., 1993).


Dendritic BC1 RNA in translational control mechanisms.

Wang H, Iacoangeli A, Lin D, Williams K, Denman RB, Hellen CU, Tiedge H - J. Cell Biol. (2005)

Translation in X. laevis oocytes, repressed by the 3′ BC1 domain, is restored by joint replenishment with eIF4A and PABP. Luciferase mRNA (Luc) was coinjected into stage VI oocytes with ∼400 nM 3′ BC1 domain, 100 nM eIF4A, and/or 100 nM PABP. Luminescence was measured after 1 h. Only replenishment with eIF4A and PABP in combination restored 3′ BC1–repressed translation to a level that was statistically indistinguishable from unrepressed translation. Quantitative analysis of four experiments is shown (one-way ANOVA, Scheffe's multiple comparison post hoc analysis, ***, P < 0.001). The observed differences among 3′ BC1, 3′ BC1 + eIF4A, and 3′ BC1 + PABP were not statistically significant.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1828541&req=5

fig3: Translation in X. laevis oocytes, repressed by the 3′ BC1 domain, is restored by joint replenishment with eIF4A and PABP. Luciferase mRNA (Luc) was coinjected into stage VI oocytes with ∼400 nM 3′ BC1 domain, 100 nM eIF4A, and/or 100 nM PABP. Luminescence was measured after 1 h. Only replenishment with eIF4A and PABP in combination restored 3′ BC1–repressed translation to a level that was statistically indistinguishable from unrepressed translation. Quantitative analysis of four experiments is shown (one-way ANOVA, Scheffe's multiple comparison post hoc analysis, ***, P < 0.001). The observed differences among 3′ BC1, 3′ BC1 + eIF4A, and 3′ BC1 + PABP were not statistically significant.
Mentions: We used the X. laevis oocyte system for these experiments. Recombinant eIF4A and PABP were coinjected with the 3′ BC1 domain either individually or in combination (Fig. 3). Luciferase activity was used as an index for relative translational efficiency; this efficiency was significantly reduced in the presence of the 3′ BC1 domain. Supplementation with eIF4A or PABP alone resulted in a moderate recovery of translation; however, this recovery failed to reach statistical significance (Fig. 3). In contrast, 3′ BC1–mediated repression could be overcome by concurrent titration with eIF4A and PABP in stoichiometric ratio (Fig. 3). At 100 nM of both factors, translational efficiency was restored to 87% of nonrepressed levels. (We presume that some of the injected RNA is chaperoned in living cells, i.e., is not functionally available, thus resulting in a lower requirement for rescue proteins relative to repressor.) Higher concentrations of eIF4A and PABP resulted in overtitration, i.e., failure to restore translational efficiency (Kahvejian et al., 2005). eIF4A and PABP are expressed at rather low levels in stage VI X. laevis oocytes, unlike ribosomes, eIF4G, ePAB, and other factors that are more abundant (Audet et al., 1987; Zelus et al., 1989; Stambuk and Moon, 1992; Keiper and Rhoads, 1999; Voeltz et al., 2001). Although it remains to be established whether the same two factors are also limiting at the synapse, similarities in translational control mechanisms have been noted between oocytes and neuronal microdomains (Richter, 2000). On the other hand, the target of translational repression does not necessarily have to be limiting as long as the local concentration of the repressor is sufficiently high, as is the case with BC1 RNA (Chicurel et al., 1993).

Bottom Line: We report that small untranslated BC1 RNA is a specific effector of translational control both in vitro and in vivo.A translational repression element is contained within the unique 3' domain of BC1 RNA.Thus, BC1 RNA modulates translation-dependent processes in neurons and germs cells by directly interacting with translation initiation factors.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Pharmacology, State University of New York, Health Science Center at Brooklyn, Brooklyn, NY 11203, USA.

ABSTRACT
Translational control at the synapse is thought to be a key determinant of neuronal plasticity. How is such control implemented? We report that small untranslated BC1 RNA is a specific effector of translational control both in vitro and in vivo. BC1 RNA, expressed in neurons and germ cells, inhibits a rate-limiting step in the assembly of translation initiation complexes. A translational repression element is contained within the unique 3' domain of BC1 RNA. Interactions of this domain with eukaryotic initiation factor 4A and poly(A) binding protein mediate repression, indicating that the 3' BC1 domain targets a functional interaction between these factors. In contrast, interactions of BC1 RNA with the fragile X mental retardation protein could not be documented. Thus, BC1 RNA modulates translation-dependent processes in neurons and germs cells by directly interacting with translation initiation factors.

Show MeSH
Related in: MedlinePlus