An upstream open reading frame (uORF) is an
open reading frame
In molecular biology, reading frames are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible reading frames ...
(ORF) within the
5' untranslated region (5'UTR) of an
mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein.
mRNA is ...
. uORFs can regulate
eukaryotic
The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...
gene expression
Gene expression is the process (including its Regulation of gene expression, regulation) by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, proteins or non-coding RNA, ...
. Translation of the uORF typically inhibits downstream expression of the primary ORF. However, in some genes such as yeast GCN4, translation of specific uORFs may increase translation of the main ORF.
In humans
Approximately 50% of human genes contain uORFs in their 5'UTR, and when present, these cause reductions in protein expression.
Human
peptide
Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Da or more are called proteins. Chains of fewer than twenty am ...
s derived from translated uORFs can be detected from cellular material with a
mass spectrometer
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a '' mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is us ...
.
uORFs were found in two thirds of proto-oncogenes and related proteins.
In bacteria
In
bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
, uORFs are called
leader peptides and were originally discovered on the basis of their impact on the regulation of genes involved in the synthesis or transport of
amino acids
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...
.
See also
*
Eukaryotic translation
Eukaryotic translation is the biological process by which messenger RNA is Translation (biology), translated into proteins in eukaryotes. It consists of four phases: initiation, elongation, termination, and recapping.
Initiation
Translation init ...
*
Short open reading frame
In molecular biology, reading frames are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible reading frames wil ...
*
Micropeptides
*
Leaky scanning
References
{{DEFAULTSORT:Upstream open reading frame
Gene expression
Molecular biology