On leaky scanning of AUG triplets in 5'UTR of vertebrate mRNAs
Rintaro Saito and Masaru Tomita
Abstract
Leaky scanning in eucaryotic translation initiation is a phenomenon in
which the first AUG triplet on mRNA is skipped by ribosome and
following AUG is selected as its start codon. Conditions for the
leaky scanning to occur are still not clearly understood. Previous
in vitro experiments demonstrated that insertion of another AUG
triplet closely after a start codon often triggers leaky scanning. We
have conducted comprehensive computer analyses of nucleotide sequences
around start codons and skipped AUG triplets using vertebrate mRNA
sequences in the GenBank database.
Results:
Sequences around start codons show consensus stronger than sequences
around skipped AUGs. Contrary to previous in vitro results,
we observe no significant increase of leaky scanning in cases where
the two AUG triplets are located close to each other. In these cases,
on the other hand, we found a stronger nucleotide consensus around the
start codon. More specifically, nucleotide consensus at position -3
is particularly strong in cases when two AUGs are separated by 5
bases. This strong nucleotide pattern around the start codon
presumably offsets potential increase of leaky scanning caused by the
closely located AUG triplet.
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