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Preferential translation of Hsp83 in Leishmania requires a thermosensitive polypyrimidine-rich element in the 3′ UTR and involves scanning of the 5′ UTR. RNA

Department of Life Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel.
RNA (Impact Factor: 4.94). 02/2010; 16(2):364-74. DOI: 10.1261/rna.1874710
Source: PubMed

ABSTRACT

Heat shock proteins (HSPs) provide a useful system for studying developmental patterns in the digenetic Leishmania parasites, since their expression is induced in the mammalian life form. Translation regulation plays a key role in control of protein coding genes in trypanosomatids, and is directed exclusively by elements in the 3' untranslated region (UTR). Using sequential deletions of the Leishmania Hsp83 3' UTR (888 nucleotides [nt]), we mapped a region of 150 nt that was required, but not sufficient for preferential translation of a reporter gene at mammalian-like temperatures, suggesting that changes in RNA structure could be involved. An advanced bioinformatics package for prediction of RNA folding (UNAfold) marked the regulatory region on a highly probable structural arm that includes a polypyrimidine tract (PPT). Mutagenesis of this PPT abrogated completely preferential translation of the fused reporter gene. Furthermore, temperature elevation caused the regulatory region to melt more extensively than the same region that lacked the PPT. We propose that at elevated temperatures the regulatory element in the 3' UTR is more accessible to mediators that promote its interaction with the basal translation components at the 5' end during mRNA circularization. Translation initiation of Hsp83 at all temperatures appears to proceed via scanning of the 5' UTR, since a hairpin structure abolishes expression of a fused reporter gene.

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Available from: Idan Gabdank, Dec 13, 2013
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    • "However, the steady-state level of various HSP transcripts is regulated by post-transcriptional mechanisms, including RNA stability and translational control. For example, the 3′UTR of Leishmania and Trypanosoma brucei HSP70 confers increased transcript stability under stress conditions (Lee, 1998; Quijada et al., 2000), as does the 3′UTR of Leishmania HSP90 that is also required for preferential translation during stress (Zilka et al., 2001; David et al., 2010). This regulation relies on the interaction of trans-acting RNA-binding proteins that recognize cis-acting elements [reviewed in Kramer and Carrington (2011)]. "
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    • "Fine deletions finally identified a regulatory element of 30 nucleotides (positions 312–341), containing a stretch of polypyrimidines. This region was shown to be part of an RNA structure that was predicted with high probability [79], using the UNAfold algorithm [80]. A biophysical evaluation of the mRNA melting curves was performed to examine the role of secondary structures in the regulatory region. "
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