Were RNA replication and translation directly coupled in the RNA (+protein?) world?

✍ Scribed by Karl H.J. Gordon

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 429 KB
• Volume: 173
• Category: Article
• ISSN: 0022-5193
• DOI: 10.1006/jtbi.1995.0054

✦ Synopsis

The ribosome is proposed to have evolved from an ancestor that simultaneously replicated and translated template RNA. At its decoding site, this ancestor to the ribosome carried a ribozyme that assembled product RNA by sequentially ligating anticodon triplets excised from tRNAs. This ribozyme was the ancestor of the Group I introns, which are still present on some ribosomal RNA precursors. Coupling of reversible RNA replication by transesterification with the thermodynamically favourable process of transpeptidation provides a rationale for the evolution of the complete ribosome as a replicase for large RNAs in the RNA (+protein?) world. A detailed and experimentally verifiable mechanism can be proposed for simultaneous replication and translation. Sequence requirements for recognition of the decoding complex as a substrate helix by these ribozymes are consistent with earlier models for the origin of the genetic code, but require an indirect mode for ribosomal self-replication. This proposal has the potential to explain the location of Group I introns in the anticodon loops of some tRNAs. * Modified from Turmel et al. (1993). † References are given in brackets after the name of the organism. These are: (1) Turmel et al.,