A cis-acting code in selenoprotein mRNAs dictates selenocysteine incorporation

Project: Research projectResearch Project

Description

Selenium, an essential trace element, is incorporated into proteins as selenocysteine (Sec).There are twenty-five selenoproteins in humans, which play a variety of critical roles in healthand disease. The proper expression of the selenoproteome is important for the normal functionof the cardiovascular, endocrine, immune, muscular, and nervous systems. Sec is encoded byUGA, which normally signals the termination of protein synthesis. The recoding of UGA as Secduring translation depends on the Sec Insertion Sequence (SECIS) element in the 3' UTR of theselenoprotein mRNA. In the absence of a SECIS, the ribosome terminates at the UGA andproduces a truncated protein, which lacks Sec. Substantial progress has been made inelucidating the role of the SECIS in dictating the expression of the selenoproteome. However,much remains to be learned about how the efficiency of Sec incorporation is regulated and howthe ribosome discriminates between the UGA/Sec codon and the authentic stop codon. Thesecentral questions are particularly critical for understanding the biosynthesis of Selenoprotein S(SelS) and other selenoproteins that contain a C-terminal Sec residue, as the UGA/Sec codon isonly a few nucleotides upstream of the stop codon. Our results suggest that the production offull-length SelS and the truncated protein that lacks Sec is highly regulated. We identified twosequences outside of the SECIS element in the SelS 3' UTR that either promote or inhibit Secincorporation. Both of these regions interact with unknown proteins. We also provide evidencethat SelS and other selenoprotein mRNAs contain the modified nucleotide pseudouridine (?) invivo. The central hypothesis of this proposal is that 3' UTR sequences outside of the SECIS andthe modified nucleotide ? are part of the cis-acting code in selenoprotein mRNAs that regulatesthe efficiency of Sec incorporation. In this proposal, we will fully define the role of the proximalstem-loop in the SelS 3' UTR in promoting Sec insertion and test the hypothesis that otherselenoproteins, which contain a C-terminal Sec are regulated by a similar mechanism. We willidentify the sequence in the distal part of the SelS 3'UTR that inhibits Sec insertion as well asthe proteins that bind to this region to mediate repression. Finally, we will define the ?landscape of the selenoprotein transcriptome and test the hypothesis that Sec may be encodedby ?GA in endogenous selenoprotein mRNAs. We expect that our studies will identify noveldeterminants that regulate the expression of the selenoproteome. Our research will also have abroad impact by providing new insight into the role of mRNA modifications in mammalian cells.
StatusActive
Effective start/end date7/1/164/30/20

Funding

  • National Institutes of Health: $356,625.00

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Selenoproteins
Selenocysteine
Messenger RNA
3' Untranslated Regions
Terminator Codon
Insertional Mutagenesis
DNA Transposable Elements
Nucleotides
Proteins
Ribosomes
Pseudouridine
Protein S
Trace Elements
Selenium