Table 1.

Selected studies on approaches to 5′ UTR identification and optimization.

UTR Sequence Origin	Key Findings	Source
Endogenous sequences	Human α-globin or β-globin based UTRs due to highly stable expression	[41]
	UTRs based on Cytochrome b-245 alpha chain (CYBA) combinations	[42]
	5′ UTR based on human hydroxysteroid 17-beta dehydrogenase 4 gene	[40]
	Endogenous 5′ and 3′ UTR selection and combination for de novo UTR design	[39]
Exogenous sequences	Library of over one million 5′ UTR variants with random 10-nucleotide sequence variation reveals dynamic sequence feature of 5′ UTRs that control mRNA translatability	[43]
	Library of 280,000 randomized 5′ UTR to build predictive models for translation by directing specific levels of ribosome loading	[37]
	5′ UTR based on synthetic sequences with high ribosomal loading calculations	[38]