uORFs, reinitiation and alternative translation start sites in human mRNAs

It is known that eukaryotic ribosomes are able to translate small ORFs and reinitiate translation at downstream start codons. However, this mechanism is widely considered to be inefficient and it is not commonly taken into account. We compiled a sample of human mRNAs containing small upstream ORFs overlapping with annotated protein coding sequences. Statistical analysis supported the hypothesis on reinitiation of translation at downstream AUG codons and functional significance of potential alternative ORFs. It may be assumed that some 5′UTR-located upstream ORFs can deliver ribosomes to alternative translation starts, and they should be taken into consideration in the prediction of human mRNA coding potential.