 | Judith Canabal University of Puerto Rico, Río Piedras (Biology '08)Mentor(s)Paul Copeland, Ph.D. Department of Molecular Genetics, Microbiology and Immunology University of Medicine and Dentistry of New Jersey |
| ||
| Characterization of novel selenoproteins containing Alu-derived components of selenocysteine incorporation. | ||
| Selenocysteine (Sec) is incorporated at select and in-frame UGA codons during translation of mRNAs containing a SECIS mRNA element. This process requires two trans-acting factors: 1) the SECIS Binding Protein (SBP2), which interacts with the SECIS element and ribosome individually, and 2) the elongation factor specific for Sec (eEFSec), which binds and delivers the Sec-tRNASec to the ribosomal A-site. Alu elements are repetitive sequences found in the genomes of primates and humans that have no known function. Although they are considered “junk DNA”, three Alu-containing genes, Bx107421, an ORF of unknown function, mitochondrial ribosome protein L48 (or mtL48) and the check-point kinase CHK2, contained sequences predicted as selenocysteine insertion sequence (SECIS) elements. Gel shifting and UV cross-linking experiments have shown that the two Alu SECIS elements interact specifically with SBP2. Furthermore, an SBP2-dependent luciferase assay suggests that the Bx107421 SECIS element supports Sec incorporation in vitro, but not MtL48. Point mutations and deletions in the SBP2 binding site of Bx107421 SECIS showed specific interaction. Together, these results demonstrate that the Bx107421 SECIS element may be functional in vivo, which supports the idea that Alu sequences may have played an important role in the evolution of novel selenoproteins. |