title: Spacer-length dependence of programmed -1 or -2 ribosomal frameshifting on a U6A heptamer supports a role for messenger RNA (mRNA) tension in frameshifting.
abstract: Programmed -1 ribosomal frameshifting is employed in the expression of a number of viral and cellular genes. In this process, the ribosome slips backwards by a single nucleotide and continues translation of an overlapping reading frame, generating a fusion protein. Frameshifting signals comprise a heptanucleotide slippery sequence, where the ribosome changes frame, and a stimulatory RNA structure, a stem-loop or RNA pseudoknot. Antisense oligonucleotides annealed appropriately 3' of a slippery sequence have also shown activity in frameshifting, at least in vitro. Here we examined frameshifting at the U6A slippery sequence of the HIV gag/pol signal and found high levels of both -1 and -2 frameshifting with stem-loop, pseudoknot or antisense oligonucleotide stimulators. By examining -1 and -2 frameshifting outcomes on mRNAs with varying slippery sequence-stimulatory RNA spacing distances, we found that -2 frameshifting was optimal at a spacer length 1-2 nucleotides shorter than that optimal for -1 frameshifting with all stimulatory RNAs tested. We propose that the shorter spacer increases the tension on the mRNA such that when the tRNA detaches, it more readily enters the -2 frame on the U6A heptamer. We propose that mRNA tension is central to frameshifting, whether promoted by stem-loop, pseudoknot or antisense oligonucleotide stimulator.
authors: Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
authors: Zhaoru
authors: Z
authors: Lin
authors: Robert J C
authors: RJ
authors: Gilbert
authors: Ian
authors: I
authors: Brierley
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D018965:Frameshifting, Ribosomal; D013058:Mass Spectrometry; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000737:chemistry* / Q000378:metabolism; D014162:Transfection
chemical_list: D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger