Key result
Deletion of the C-terminal dimerization domain of the La autoantigen abrogated its ability to enhance translation of poliovirus RNA and HIV TAR-element-containing mRNA in vitro.
The La autoantigen requires a specific C-terminal dimerization domain to homodimerize and enhance the translation of viral RNAs.
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Identifies La dimerization as essential for viral mRNA translation; leaves open therapeutic targeting in vivo.
The La autoantigen is an RNA-binding protein that is involved in initiation and termination of RNA polymerase III transcription. It also binds several viral RNAs, including those of poliovirus and human immunodeficiency virus (HIV). Binding of the La protein to these RNAs enhances their translation in vitro (K. Meerovitch, Y.V. Svitkin, H.S. Lee, F. Lejbkowicz, D.J. Kenan, E.K.L. Chan, V.L. Agol, J.D. Keene, and N. Sonenberg, J. Virol. 67:3798-3807, 1993, and Y.V. Svitkin, A. Pause, and N. Sonenberg, J. Virol. 68:7001-7007, 1994). Here, a functional domain in the carboxy-terminal half of La that is distinct from the RNA-binding domain is described. Deletion of this domain abrogated the ability of La protein to enhance translation of poliovirus RNA and a hybrid HIV trans-activation-response element-chloramphenicol acetyltransferase mRNA. Far-Western assays indicated that the La protein homodimerized in vitro, and the C-terminal deletions that caused a loss of activity in translation also abrogated the dimerization signal. Gel filtration chromatography of recombinant La protein confirmed that La protein exists as a dimer under native conditions. Addition of the purified dimerization domain resulted in a loss of translation stimulatory activity of La protein in cell-free-translation reactions.
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Craig et al. (1997) studied this question. La autoantigen C-terminal dimerization domain deletion vs. Wild-type La autoantigen was evaluated on Translation enhancement of poliovirus RNA and HIV TAR-element-containing mRNA in vitro. Deletion of the C-terminal dimerization domain of the La autoantigen abrogated its ability to enhance translation of poliovirus RNA and HIV TAR-element-containing mRNA in vitro.
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