Oligopyrimidine tract at the 5' end of mammalian ribosomal protein mRNAs is required for their translational control.

Abstract

Mammalian ribosomal protein (rp) mRNAs are subject to translational control, as illustrated by their selective release from polyribosomes in growth-arrested cells and their underrepresentation in polysomes in normally growing cells. In the present experiments, we have emined whether the translational control of rp mRNAs is attributable to the distinctive features of their 5' untranslated region, in particular to the oligopyrimidine tract adjacent to the cap structure. Murine lymphosarcoma cells were transfected with chimeric genes consisting of selected regions of rp mRNA fused to non-rp mRNA segments, and the translational efficiency of the resulting chimeric mRNAs was assessed in cells that either were growing normally or were growth-arrested by glucocorticoid treatment. We observed that translational control of rpL32 mRNA was abolished when its 5' untranslated region was replaced by that of .8-actin. At the same time, human growth hormone (hGH) mRNA acquired the typical behavior of rp mRNAs when it was preceded by the first 61 nucleotides of rpL30 mRNA or the first 29 nucleotides of rpS16 mRNA. Moreover, the translational control of rpSl6-hGH mRNA was abolished by the substitution of purines into the pyrimidine tract or by shortening it from eight to six residues with a concomitant cytidine -* uridine change at the 5' terminus.These results indicate that the 5'-terminal pyrimidine tract plays a critical role in the translational control mechanism. Possible factors that might interact with this translational cis regulatory element are discussed.Control at the translational level plays a dominant role in the regulated expression of eukaryotic ribosomal protein (rp) genes under a variety of conditions (1-3). These include: early development of Dictyostelium discoideum (4), Drosophila melanogaster (5)

Crosslinking of Ribosomal Proteins to RNA in Maize Ribosomes by UV-B and Its Effects on Translation

“…In evaluating the oligopyrimidine tracks we found no strict consensus motif, although some transcripts have the same 5# TOP sequence. This is also true for the vertebrate ribosomal protein 5# TOP sequences (Levy et al, 1991). Combined with the observations that UV-B stimulates phosphorylation of S6 and its kinase and selective translation of some ribosomal proteins, the presence of 5# TOP sequences in some maize ribosomal protein transcripts suggests that translational control of these proteins by UV-B in plants could utilize mechanisms similar to those in mammalian cells.…”

“…One mechanism permitting selective translation of eukaryotic mRNA requires an oligopyrimidine tract at the 5# terminus. This element usually consists of a cytidine residue at the cap site followed by an uninterrupted sequence of 7 to13 pyrimidine nucleotides (Levy et al, 1991). The 5# TOP sequence is essential for the translational regulation observed (Meyuhas et al, 1997).…”

Plant L10 Ribosomal Proteins Have Different Roles during Development and Translation under Ultraviolet-B Stress

“…Consequently, synthesis of both RNA and protein components of the ribosome is highly regulated. In vertebrates, a characteristic motif of mRNAs encoding for the 80S ribosomal proteins and some translational factors is a 5# terminal oligopyrimidine (5#TOP) sequence that is necessary for growth-associated translational regulation (Levy et al, 1991;Avni et al, 1997;Iadevaia et al, 2008). Only the RPL10B transcript in the RPL10 family has a 5#TOP sequence (Supplemental Table S4); however, the role of the 5#TOP motif in the regulation of translation has not been demonstrated in plants.…”

Lipoplex-induced hemagglutination: potential involvement in intravenous gene delivery

“…An Escherichia coli containing the plasmid pCMV-GH (a 4.8 kbp plasmid containing a gene coding for human growth hormone, hGH) 43 was a gift of Dr O Meuhas, Department of Biochemistry, Hebrew University. 43 DNA was purified using the plasmid Mega kit of QIAGEN.…”