Abstract: The 3′ untranslated region (3′_UTR) of eukaryotic transcripts plays an important role in regulating gene expression on post_transcriptional level. 3′end processing signals which instruct the 3′ end processing exist in 3′_UTR. 3′_UTR not only controls mRNA stability and the rate of mRNA degradation, but also helps to recognize UGA codon which directs the incorporation of rareselenocysteine into proteins. Still, many other signals existing in 3′_UTR determine mRNA localization, regulate translation initiation and translation efficiency as well as translation time, sites, etc.