title: An evolutionarily conserved element in initiator tRNAs prompts ultimate steps in ribosome maturation.
abstract: Ribosome biogenesis, a complex multistep process, results in correct folding of rRNAs, incorporation of >50 ribosomal proteins, and their maturation. Deficiencies in ribosome biogenesis may result in varied faults in translation of mRNAs causing cellular toxicities and ribosomopathies in higher organisms. How cells ensure quality control in ribosome biogenesis for the fidelity of its complex function remains unclear. Using Escherichia coli, we show that initiator tRNA (i-tRNA), specifically the evolutionarily conserved three consecutive GC base pairs in its anticodon stem, play a crucial role in ribosome maturation. Deficiencies in cellular contents of i-tRNA confer cold sensitivity and result in accumulation of ribosomes with immature 3' and 5' ends of the 16S rRNA. Overexpression of i-tRNA in various strains rescues biogenesis defects. Participation of i-tRNA in the first round of initiation complex formation licenses the final steps of ribosome maturation by signaling RNases to trim the terminal extensions of immature 16S rRNA.
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, 560012, India.
authors.forename: Sunil
authors.initials: S
authors.lastname: Shetty
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, 560012, India; Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, 560064, India varshney@mcbl.iisc.ernet.in.
authors.forename: Umesh
authors.initials: U
authors.lastname: Varshney
mesh_terms: D000926:Anticodon / Q000235:genetics; D017124:Conserved Sequence; D004843:Epistasis, Genetic; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D020862:GC Rich Sequence; D009154:Mutation; D010448:Peptide Initiation Factors / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics; D012343:RNA, Transfer / Q000737:chemistry / Q000235:genetics*; D020218:Response Elements; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D000926:Anticodon; D010448:Peptide Initiation Factors; D011500:Protein Synthesis Inhibitors; D012336:RNA, Ribosomal, 16S; D012343:RNA, Transfer
keywords: 16S rRNA maturation; 3GC base pairs; RNase PH/RNAse R; cold sensitivity; ribosome biogenesis