Probing Selenoprotein Translation by Ribosome Profiling
Selenoproteins with known functions are oxidoreductase enzymes that serve roles in maintaining cellular redox balance, reproductive health, thyroid hormone metabolism, development, and immune functions. Unique to selenoprotein biosynthesis is the requirem
- PDF / 601,323 Bytes
- 13 Pages / 439.37 x 666.14 pts Page_size
- 28 Downloads / 150 Views
Probing Selenoprotein Translation by Ribosome Profiling Michael T. Howard
Abstract Selenoproteins with known functions are oxidoreductase enzymes that serve roles in maintaining cellular redox balance, reproductive health, thyroid hormone metabolism, development, and immune functions. Unique to selenoprotein biosynthesis is the requirement during translation to redefine an in-frame UGA codon to encode for selenocysteine rather than terminate translation. This noncanonical translation event is a bottleneck in selenoprotein synthesis and subject to gene-specific regulation. Here, the application of ribosome profiling, which involves deep sequencing of ribosome protected mRNA fragments, to examine mechanisms of selenoprotein biosynthesis will be discussed. The ability of this technique to quantify ribosome abundance and position, at codon resolution, on selenoprotein mRNAs has provided important insight into long-standing questions regarding the efficiency and regulation of selenocysteine incorporation as well as provoking new questions for future investigations. Keywords Recoding • Ribosome footprint • Ribosome pausing • Ribosome profiling • Selenium • Selenocysteine • Selenoproteins • Translation
3.1
Introduction
Selenium (Se) is incorporated into a small number of mammalian proteins, encoded by ~25 mammalian genes, in the form of the amino acid selenocysteine (Sec) [1, 2]. In addition to the beneficial physical properties that Sec confers to selenoproteins, it is unique among amino acids in that its incorporation occurs during translation when a UGA codon, normally specifying translational termination, is decoded by Sec-tRNA[Ser]Sec as Sec. The process of UGA redefinition and Sec insertion during translation is thought to be inefficient due, at least in part, to the requirement for
M.T. Howard (*) Human Genetics, University of Utah, 15 N. 2030 E, Room 7110, Salt Lake City, UT 84112, USA e-mail: [email protected] © Springer Science+Business Media, LLC 2016 D.L. Hatfield et al. (eds.), Selenium, DOI 10.1007/978-3-319-41283-2_3
25
26
M.T. Howard
specialized Sec insertion factors to “reprogram” the ribosome and recruit SectRNA[Ser]Sec, in a process that competes with translational termination. Studies by a number of laboratories have uncovered the core components of the Sec incorporation machinery. In eukaryotes, these include the cis-acting Sec insertion sequence elements (SECIS) found in the 3′ UTRs of all selenoprotein mRNAs [3–5] and the Sec redefinition elements (SREs), which reside adjacent to a subset of UGA-Sec codons [6–8]. Several trans-acting factors are also required including Sec-tRNA[Ser]Sec and the proteins involved in tRNA maturation and Sec synthesis, the Sec-tRNA[Ser]Sec elongation factor (eEFSec) that delivers Sec-tRNA[Ser]Sec to the ribosome [9–11], and finally, the SECIS binding protein 2 (Secisbp2) [12, 13]. The latter is thought to have an essential role in Sec-tRNA[Ser]Sec recruitment to the ribosome as well as an independent role in regulating selenoprotein mRNA stability [14]. In additi
Data Loading...
