Chemical conversion of cytidine residues into 4-thiouridines in yeast tRNAPhe. Determination of the modified cytidines

Use of specific chemical reagents for detection of modified nucleotides in RNA

Naturally occurring cellular RNAs contain an impressive number of chemically distinct modified residues which appear posttranscriptionally, as a result of specific action of the corresponding RNA modification enzymes. Over 100 different chemical modifications have been identified and characterized up to now. Identification of the chemical nature and exact position of these modifications is typically based on 2D-TLC analysis of nucleotide digests, on HPLC coupled with mass spectrometry, or on the use of primer extension by reverse transcriptase. However, many modified nucleotides are silent in reverse transcription, since the presence of additional chemical groups frequently does not change base-pairing properties. In this paper, we give a summary of various chemical approaches exploiting the specific reactivity of modified nucleotides in RNA for their detection.

A consonant model of the tRNA-ribosome complex during the elongation cycle of translation

Chemical and photochemical affinity techniques have been used extensively to determine the positions of the tRNA binding sites on the Escherichia coli ribosome. Recent advances in our understanding of ribosome structure and function prompted us to critically review the data that have accumulated on tRNA-ribosome cross-links. As a result, we propose a new model of the tRNA-ribosome complex that accounts for nearly all of the pertinent evidence.