The present annotation of the
S. cerevisiae
genome at
SGD
contains 969 annotated ORFs which overlap other ORFs, ARS elements,
snRNA genes, tRNA genes or transposon sequences. There are 387 pairs,
29 triplets, 5 quadruplets and 1 quintuplet of overlapping ORFs. 5
ORFs overlap with an ARS element, 7 with a snRNA gene, 7 with a tRNA
gene, and 63 with a transposon sequence (Ty, delta, tau, omicron),
which were treated as independent ORFs in the project. A substantial
number of these annotated ORFs likely represent computational ORFs
without any coding potential. Often in this situation, there is no
evidence about whether either or both ORFs encode for a protein or
not.
Click here for the Overlapping_features
list.
1105 essential ORFs were also screened to see if there were possible
ORFs within ORFs. Out of 387 pairs of overlapping ORFs, 56 pairs
were found where both ORFs gave a lethal phenotype when disrupted,
while in 12 cases, only of one of the two show the same effect.
Similar data was obtained when looking at overlaps involving 3 and
4 ORFs. We suggest that in overlapping cases the deletion of a computational
ORF may lead to the partial or lethal deletion of the corresponding
essential ORF and we point this out as caveat to be aware of when
dealing with overlapping ORF phenotypes. Only 3 out of 82 ORFs overlapping
with non ORF features are essential: YAL003W (EFB1), YFR031C (SMC2),
and YGL145W (TIP20)). 2 overlap with an ARS element and 1 with a
snRNA. This suggests that deletions of ARS, snRNAs, tRNAs or transposon
associated ORFs have a propensity to be viable. Finally, none of
the deletions of ORFs overlapping transposon elements (63) is lethal,
though many of these latter ORFs may also represent computational
ORFs.
Click here for the Overlapping
ORFs essential list.