News and Publications

Modulation of mRNA Translation by Direct Interactions With Ribosomes

V.P. Mauro, B.A. Cunningham, P. Tranque, M.C.-Y. Hu, G.M. Edelman

Our recent analysis of the nucleic acid databases led to the observation that eukaryotic mRNAs contain sequences that resemble rRNA. On the basis of these observations, we hypothesized that rRNA-like sequences would mediate interactions between mRNA and ribosomes; sequence similarities or "sense" matches might mimic rRNA and bind ribosomal proteins, whereas complementary or "antisense" sequences might form base pairs with rRNA. Because ribosomes are the cellular structures that translate mRNAs into protein, we further postulated that these interactions would directly affect translation.

To determine whether complementarity to rRNA would allow some RNAs to bind ribosomes by base-pairing to the rRNA, we used photochemical cross-linking to examine the accessibility of the ribosome to various RNA probes. We found that probes with 100% complementarity to 5 different regions of the 18S or 28S rRNAs cross-linked specifically to the corresponding rRNA. In addition, cross-linking experiments with 55 probes that were 72--100% complementary to the 18S rRNA indicated that many different mRNA probes could bind specifically to the 18S rRNA. RNase H cleavage showed that 4 such probes cross-linked to complementary regions of the 18S rRNA.

To examine the effects of rRNA sequence complementarity on translation, we used the mRNA that encodes ribosomal protein S15. This mRNA is complementary to the 18S rRNA at 20 of 22 nucleotides. RNA from S15-luciferase fusion constructs with various degrees of complementarity to the 18S rRNA were translated in vitro. A strong inverse correlation was found between the degree of complementarity to the 18S rRNA and the luciferase activity.

To help determine whether matches to the rRNA in the sense orientation allow some mRNAs to bind ribosomal proteins, we are generating antibodies to the individual ribosomal proteins. These antibodies will be used to test for inhibition of binding of mRNA segments to ribosomes. In the course of these studies, we have found unusual variations in some ribosomal proteins that may reflect the ability of the proteins to bind rRNA or mRNA. These ribosomal proteins and segments of them are being expressed as recombinant proteins to test the ability of the original proteins or segments to bind RNA and affect translation.

The results of our studies suggest that direct binding of particular mRNAs to ribosomes may be a mechanism of translational control. We are continuing to examine the interactions of mRNAs with ribosomes and are testing the effects of these interactions on translation.

PUBLICATIONS

Denda, S., Müller, U., Crossin, K.L., Erickson, H.P., Reichardt, L.F. Utilization of a soluble integrin-alkaline phosphatase chimera to characterize integrin /alpha/₈ß₁ interactions with tenascin: Murine /alpha/₈ß₁ binds to the RGD site in tenascin-C fragments, but not to native tenascin. Biochemistry 37:5464, 1998.

Edelman, G.M., Jones, F.S. Gene regulation of cell adhesion: A key step in neural morphogenesis. Brain Res. Rev. 26:337, 1998.

Greenspan, R.J. A kinder, gentler analysis of behavior: Dissection gives way to modulation. Curr. Opin. Neurobiol. 7:805, 1997.

Holst, B.D., Vanderklish, P.W., Krushel, L.A., Zhou, W., Langdon, R.B., McWhirter, J.R., Edelman, G.M., Crossin, K.L. Allosteric modulation of AMPA-type glutamate receptors increases activity of the promoter for the neural cell adhesion molecule, N-CAM. Proc. Natl. Acad. Sci. U.S.A. 95:2597, 1998.

Kallunki, P., Edelman, G.M., Jones, F.S. The neural restrictive silencer element can act as both a repressor and enhancer of L1 cell adhesion molecule gene expression during postnatal development. Proc. Natl. Acad. Sci. U.S.A. 95:3233, 1998.

Kallunki, P., Edelman, G.M., Jones, F.S. Tissue-specific expression of the L1 cell adhesion molecule is modulated by the neural restrictive silencer element. J. Cell Biol. 138:1343, 1997.

Kane, N.S., Robichon, A., Dickinson, J.A., Greenspan, R.J. Learning without performance in PKC-deficient Drosophila. Neuron 18:307, 1997.

Krushel, L.A., Tai, M.-H., Cunningham, B.A., Edelman, G.M., Crossin, K.L. Neural cell adhesion molecule (N-CAM) domains and intracellular signaling pathways involved in the inhibition of astrocyte proliferation. Proc. Natl. Acad. Sci. U.S.A. 95:2592, 1998.

Maleszka, R., Lupas, A., Hanes, SD., Miklos, G.L. The dodo gene family encodes a novel protein involved in signal transduction and protein folding. Gene 203:89, 1997.

Phillips, G.R., Krushel, L.A., Crossin, K.L. Developmental expression of two rat sialyltransferases that modify that neural cell adhesion molecule, N-CAM. Dev. Brain Res. 102:143, 1997.

Phillips, G.R., Krushel, L.A., Crossin, K.L. Domains of tenascin involved in glioma migration. J. Cell Sci. 111:1095, 1998.