N. Suraweera et al., Conservation of mononucleotide repeats within 3 ' and 5 ' untranslated regions and their instability in MSI-H colorectal cancer, ONCOGENE, 20(51), 2001, pp. 7472-7477
Messenger RNA contains untranslated 3' and 5' regions (3' and 5' UTRs) with
sequence elements that are essential for the regulation of gene expression
. A systematic search of GenBank revealed a large number of mononucleotide
repeats within these UTRs. We selected 35 such mononucleotide repeats rangi
ng in length from 15 bp to 32 bp and analysed their size in a series of 60
normal individuals. The conservation of repeats correlated inversely to the
ir length, with longer repeats generally being more polymorphic than shorte
r repeats, irrespective of 3' or 5' location. Several long repeats were ide
ntified however to be monomorphic and we postulate that their conservation
may be due to selective pressures relating to a possible functional role. W
e analysed 19 conserved UTR repeats in 117 colorectal cancers (CRC), 43 of
which had defective mismatch repair characterized by widespread microsatell
ite instability (MSI-H). The UTR repeats were very often deleted in MSI-H t
umors, with the length of deletion being proportional to the size of the re
peat. Because of the high frequency of deletion observed in the conserved U
TR repeats of MSI-H tumors, these could serve as a useful model for the stu
dy of possible changes in gene expression resulting from such mutations.