title: The UGG Isoacceptor of tRNAPro Is Naturally Prone to Frameshifts.
abstract: Native tRNAs often contain post-transcriptional modifications to the wobble position to expand the capacity of reading the genetic code. Some of these modifications, due to the ability to confer imperfect codon-anticodon pairing at the wobble position, can induce a high propensity for tRNA to shift into alternative reading frames. An example is the native UGG isoacceptor of E. coli tRNAPro whose wobble nucleotide U34 is post-transcriptionally modified to cmo5U34 to read all four proline codons (5'-CCA, 5'-CCC, 5'-CCG, and 5'-CCU). Because the pairing of the modified anticodon to CCC codon is particularly weak relative to CCA and CCG codons, this tRNA can readily shift into both the +1 and +2-frame on the slippery mRNA sequence CCC-CG. We show that the shift to the +2-frame is more dominant, driven by the higher stability of the codon-anticodon pairing at the wobble position. Kinetic analysis suggests that both types of shifts can occur during stalling of the tRNA in a post-translocation complex or during translocation from the A to the P-site. Importantly, while the +1-frame post complex is active for peptidyl transfer, the +2-frame complex is a poor peptidyl donor. Together with our recent work, we draw a mechanistic distinction between +1 and +2-frameshifts, showing that while the +1-shifts are suppressed by the additional post-transcriptionally modified m1G37 nucleotide in the anticodon loop, the +2-shifts are suppressed by the ribosome, supporting a role of the ribosome in the overall quality control of reading-frame maintenance.
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA. howard.gamper@jefferson.edu.
authors.forename: Howard B
authors.initials: HB
authors.lastname: Gamper
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA. isao.masuda@jefferson.edu.
authors.forename: Isao
authors.initials: I
authors.lastname: Masuda
authors.affiliation: Faculty of Medicine, Bar-Ilan University, Henrietta Szold 8, Safed 1311502, Israel. milana.morgenstern@biu.ac.il.
authors.forename: Milana
authors.initials: M
authors.lastname: Frenkel-Morgenstern
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA. ya-ming.hou@jefferson.edu.
authors.forename: Ya-Ming
authors.initials: YM
authors.lastname: Hou
mesh_terms: D020029:Base Pairing; D003062:Codon / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D016368:Frameshift Mutation; D012333:RNA, Messenger / Q000235:genetics; D012361:RNA, Transfer, Pro / Q000235:genetics*
chemical_list: D003062:Codon; D012333:RNA, Messenger; D012361:RNA, Transfer, Pro
keywords: +1-frameshift; +2-frameshift; cmo5U34; m1G37-tRNA; ribosome; slippery mRNA sequence; translation