Evolutionary changes of the target sites of two microRNAs encoded in the XXXX gene cluster of @entity238 and other insect species.

@entity4564 @entity4534 @entity17809 @entity377 @entity238 @entity72090 @entity4565 @entity72091
MicroRNAs (miRs) are noncoding RNAs that regulate gene expression at the post-transcriptional level. In animals, the target sites of a @entity72090 are generally located in the 3' untranslated regions (UTRs) of messenger RNAs. However, how the target sites change during evolution is largely unknown. @entity72091 and @entity72091 as are known to regulate the expression of two @entity17809 genes, @entity4534 and @entity4564 , in @entity238 . We have therefore studied the evolutionary changes of these two @entity72090 genes and their target sites of the @entity17809 genes in @entity238 , other insect species, and Daphnia. Our homology search identified a single copy of each @entity72090 gene located in the same genomic position of the @entity17809 gene cluster in all species examined. The seed @entity377 sequence was also the same for all species. Searching for the target sites in all @entity17809 genes, we found several target sites of @entity72091 and @entity72091 as in @entity4565 in addition to @entity4534 and @entity4564 in most insect species examined. Our phylogenetic analysis of target sites in @entity4534 , @entity4564 , and @entity4565 showed that the old target sites, which existed before the divergence of the 12 @entity238 species, have been well maintained in most species under purifying selection. By contrast, new target sites, which were generated during @entity238 evolution, were often lost in some species and mostly located in unalignable regions of the 3' UTRs. These results indicate that these regions can be a potential source of generating new target sites, which results in multiple target genes for each @entity72090 in animals.
