Human acetyl-coA cholesterol acyltransferase ( ACAT1) gene produces a chimeric mRNA through the interchromosomal processing of two discontinuous

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

s transcribed from chromosomes 1 and 7. This chimeric mRNA uses AUG as a translation initiation codon to produce the normal 50- kDa ACAT1 protein but used an alternative translation initiation codon, GGC, to produce the novel

enzymatically Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...

active 56-kDa isoform. Mutagenesis and

mass spectrometry 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 use ...

identified the alternative initiation codon as the

start codon The start codon is the first codon of a messenger RNA (mRNA) transcript translated by a ribosome. The start codon always codes for methionine in eukaryotes and Archaea and a N-formylmethionine (fMet) in bacteria, mitochondria and plastids. The ...

for the novel 56-kDa protein and its location was mapped to a region located upstream of the AUG initiation codon. Three stem loop structures have been predicted to surround the GCC initiation codon and are known as SL1 to SL3. Mutations that disrupted these

stem-loop Stem-loop intramolecular base pairing is a pattern that can occur in single-stranded RNA. The structure is also known as a hairpin or hairpin loop. It occurs when two regions of the same strand, usually complementary in nucleotide sequence when ...

structures showed that SL1 and SL2 as required for translation initiation from the GGC codon but SL3 has no effect on translation efficiency. Translation initiation from the GGC codon was shown to be is mediated by an internal ribosome entry site (IRES) which requires SL1 located upstream of the IRES and SL2 located downstream. This study also showed that SL3 influences the choice of downstream AUG translation initiation codons that will produce the normal 50-KDa human ACAT1 protein.

References

External links

* {{Rfam, id=RF01495, name=ACAT1 RNA