Upstream Open Reading Frames as Regulators of mRNA Translation

ABSTRACT The proto-oncogene Fli-1 encodes a transcription factor of the ets family whose overexpression is associated with multiple virally induced leukemias in mouse, inhibits murine and avian erythroid cell differentiation, and induces drastic perturbations of early development in Xenopus. This study demonstrates the surprisingly sophisticated regulation of Fli-1 mRNA translation. We establish that two FLI-1 protein isoforms (of 51 and 48 kDa) detected by Western blotting in vivo are synthesized by alternative translation initiation through the use of two highly conserved in-frame initiation codons, AUG +1 and AUG +100. Furthermore, we show that the synthesis of these two FLI-1 isoforms is regulated by two short overlapping 5′ upstream open reading frames (uORF) beginning at two highly conserved upstream initiation codons, AUG −41 and GUG −37, and terminating at two highly conserved stop codons, UGA +35 and UAA +15. The mutational analysis of these two 5′ uORF revealed that each of them negatively regulates FLI-1 protein synthesis by precluding cap-dependent scanning to the 48- and 51-kDa AUG codons. Simultaneously, the translation termination of the two 5′ uORF appears to enhance 48-kDa protein synthesis, by allowing downstream reinitiation at the 48-kDa AUG codon, and 51-kDa protein synthesis, by allowing scanning ribosomes to pile up and consequently allowing upstream initiation at the 51-kDa AUG codon. To our knowledge, this is the first example of a cellular mRNA displaying overlapping 5′ uORF whose translation termination appears to be involved in the positive control of translation initiation at both downstream and upstream initiation codons.

Download Full-text

Translational regulation of the plant S-adenosylmethionine decarboxylase

Biochemical Society Transactions ◽

10.1042/bst0310424 ◽

2003 ◽

Vol 31 (2) ◽

pp. 424-427 ◽

Cited By ~ 18

Author(s):

C. Hanfrey ◽

M. Franceschetti ◽

M.J. Mayer ◽

C. Illingworth ◽

K. Elliott ◽

...

Keyword(s):

Protein Synthesis ◽

Rna Secondary Structure ◽

Translational Regulation ◽

Mrna Translation ◽

Open Reading Frames ◽

Polyamine Biosynthesis ◽

Adenosylmethionine Decarboxylase ◽

Key Enzyme ◽

Upstream Open Reading Frames ◽

Reading Frames

It is becoming apparent that control of protein synthesis by metabolites is more common than previously thought. Much of that control is exerted at the level of initiation of mRNA translation, orchestrated by upstream open reading frames (uORFs) and RNA secondary structure. S-Adenosylmethionine decarboxylase (AdoMetDC) is a key enzyme in polyamine biosynthesis and both mammalian and plant AdoMetDCs are translationally regulated by uORFs in response to polyamine levels by distinct mechanisms.

Download Full-text

Faculty Opinions recommendation of Translational control via protein-regulated upstream open reading frames.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.11312956.12315054 ◽

2011 ◽

Author(s):

Craig Smibert ◽

Alexander J Marsolais

Keyword(s):

Translational Control ◽

Open Reading Frames ◽

Upstream Open Reading Frames ◽

Reading Frames

Download Full-text

Faculty Opinions recommendation of Upstream open reading frames cause widespread reduction of protein expression and are polymorphic among humans.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1162726.624847 ◽

2009 ◽

Author(s):

Bryan Williams ◽

Michael Paul Gantier

Keyword(s):

Protein Expression ◽

Open Reading Frames ◽

Upstream Open Reading Frames ◽

Reading Frames

Download Full-text

A First Step towards Learning which uORFs Regulate Gene Expression

Journal of Integrative Bioinformatics ◽

10.1515/jib-2006-31 ◽

2006 ◽

Vol 3 (2) ◽

pp. 109-122 ◽

Cited By ~ 1

Author(s):

◽

Christopher H. Bryant ◽

Graham J.L. Kemp ◽

Marija Cvijovic

Keyword(s):

Gene Expression ◽

Inductive Logic ◽

Preliminary Evidence ◽

Open Reading Frames ◽

Yeast Saccharomyces Cerevisiae ◽

Regulate Gene Expression ◽

Integrative System ◽

Upstream Open Reading Frames ◽

Reading Frames ◽

Regulate Gene

Summary We have taken a first step towards learning which upstream Open Reading Frames (uORFs) regulate gene expression (i.e., which uORFs are functional) in the yeast Saccharomyces cerevisiae. We do this by integrating data from several resources and combining a bioinformatics tool, ORF Finder, with a machine learning technique, inductive logic programming (ILP). Here, we report the challenge of using ILP as part of this integrative system, in order to automatically generate a model that identifies functional uORFs. Our method makes searching for novel functional uORFs more efficient than random sampling. An attempt has been made to predict novel functional uORFs using our method. Some preliminary evidence that our model may be biologically meaningful is presented.

Download Full-text

Translation of ABCE1 Is Tightly Regulated by Upstream Open Reading Frames in Human Colorectal Cells

Biomedicines ◽

10.3390/biomedicines9080911 ◽

2021 ◽

Vol 9 (8) ◽

pp. 911

Author(s):

Joana Silva ◽

Pedro Nina ◽

Luísa Romão

Keyword(s):

Translational Regulation ◽

Regulatory Elements ◽

Ribosome Profiling ◽

Leader Sequence ◽

Open Reading Frames ◽

Regulatory Function ◽

Coding Sequence ◽

Abc Protein ◽

Upstream Open Reading Frames ◽

Reading Frames

ATP-binding cassette subfamily E member 1 (ABCE1) belongs to the ABC protein family of transporters; however, it does not behave as a drug transporter. Instead, ABCE1 actively participates in different stages of translation and is also associated with oncogenic functions. Ribosome profiling analysis in colorectal cancer cells has revealed a high ribosome occupancy in the human ABCE1 mRNA 5′-leader sequence, indicating the presence of translatable upstream open reading frames (uORFs). These cis-acting translational regulatory elements usually act as repressors of translation of the main coding sequence. In the present study, we dissect the regulatory function of the five AUG and five non-AUG uORFs identified in the human ABCE1 mRNA 5′-leader sequence. We show that the expression of the main coding sequence is tightly regulated by the ABCE1 AUG uORFs in colorectal cells. Our results are consistent with a model wherein uORF1 is efficiently translated, behaving as a barrier to downstream uORF translation. The few ribosomes that can bypass uORF1 (and/or uORF2) must probably initiate at the inhibitory uORF3 or uORF5 that efficiently repress translation of the main ORF. This inhibitory property is slightly overcome in conditions of endoplasmic reticulum stress. In addition, we observed that these potent translation-inhibitory AUG uORFs function equally in cancer and in non-tumorigenic colorectal cells, which is consistent with a lack of oncogenic function. In conclusion, we establish human ABCE1 as an additional example of uORF-mediated translational regulation and that this tight regulation contributes to control ABCE1 protein levels in different cell environments.

Download Full-text

Improved ribosome-footprint and mRNA measurements provide insights into dynamics and regulation of yeast translation

10.1101/021501 ◽

2015 ◽

Cited By ~ 2

Author(s):

David E Weinberg ◽

Premal Shah ◽

Stephen W Eichhorn ◽

Jeffrey A Hussmann ◽

Joshua B Plotkin ◽

...

Keyword(s):

Translational Control ◽

Nucleotide Composition ◽

Ribosome Profiling ◽

Open Reading Frames ◽

Untranslated Regions ◽

Coding Regions ◽

Genome Wide ◽

Upstream Open Reading Frames ◽

Improved Methods ◽

Reading Frames

Ribosome-footprint profiling provides genome-wide snapshots of translation, but technical challenges can confound its analysis. Here, we use improved methods to obtain ribosome-footprint profiles and mRNA abundances that more faithfully reflect gene expression in Saccharomyces cerevisiae. Our results support proposals that both the beginning of coding regions and codons matching rare tRNAs are more slowly translated. They also indicate that emergent polypeptides with as few as three basic residues within a 10-residue window tend to slow translation. With the improved mRNA measurements, the variation attributable to translational control in exponentially growing yeast was less than previously reported, and most of this variation could be predicted with a simple model that considered mRNA abundance, upstream open reading frames, cap-proximal structure and nucleotide composition, and lengths of the coding and 5′- untranslated regions. Collectively, our results reveal key features of translational control in yeast and provide a framework for executing and interpreting ribosome- profiling studies.

Download Full-text

The first and fourth upstream open reading frames in GCN4 mRNA have similar initiation efficiencies but respond differently in translational control to change in length and sequence

Molecular and Cellular Biology ◽

10.1128/mcb.8.12.5439-5447.1988 ◽

1988 ◽

Vol 8 (12) ◽

pp. 5439-5447

Author(s):

P P Mueller ◽

B M Jackson ◽

P F Miller ◽

A G Hinnebusch

Keyword(s):

Translational Control ◽

Normal Growth ◽

Open Reading Frames ◽

Regulatory Function ◽

Coding Sequences ◽

Lacz Fusions ◽

Upstream Open Reading Frames ◽

Reading Frames ◽

Starvation Conditions

The third and fourth AUG codons in GCN4 mRNA efficiently repress translation of the GCN4-coding sequences under normal growth conditions. The first AUG codon is approximately 30-fold less inhibitory and is required under amino acid starvation conditions to override the repressing effects of AUG codons 3 and 4. lacZ fusions constructed to functional, elongated versions of the first and fourth upstream open reading frames (URFs) were used to show that AUG codons 1 and 4 function similarly as efficient translational start sites in vivo, raising the possibility that steps following initiation distinguish the regulatory properties of URFs 1 and 4. In accord with this idea, we observed different consequences of changing the length and termination site of URF1 versus changing those of URFs 3 and 4. The latter were lengthened considerably, with little or no effect on regulation. In fact, the function of URFs 3 and 4 was partially reconstituted with a completely heterologous URF. By contrast, certain mutations that lengthen URF1 impaired its positive regulatory function nearly as much as removing its AUG codon did. The same mutations also made URF1 a much more inhibitory element when it was present alone in the mRNA leader. These results strongly suggest that URFs 1 and 4 both function in regulation as translated coding sequences. To account for the phenotypes of the URF1 mutations, we suggest the most ribosomes normally translate URF1 and that the mutations reduce the number of ribosomes that are able to complete URF1 translation and resume scanning downstream. This effect would impair URF1 positive regulatory function if ribosomes must first translate URF1 in order to overcome the strong translational block at the 3'-proximal URFs. Because URF1-lacZ fusions were translated at the same rate under repressing and derepressing conditions, it appears that modulating initiation at URF1 is not the means that is used to restrict the regulatory consequences of URF1 translation to starvation conditions.

Download Full-text