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Summer Research Fellowship Programme of India's Science Academies

Expression of Animalia-specific tRNA deacylase in cell types

SAYONI SAHA

National Institute of Technology Durgapur, West Bengal-713209

DR. RAJAN SANKARANARAYANAN

CSIR- Centre for Cellular and Molecular Biology, Hyderabad-500007

Abstract

Proteins are essential macromolecules of life. The biological information transfer from DNA to proteins via transcription and translation have errors associated with them. Proteins are synthesized by ribosomes with aminoacyl-tRNA as its substrate and mRNA acting as its template. Translational fidelity largely depends on the correctness of amino acid and tRNA, pairing which is done by enzymes called aminoacyl-tRNA synthetases (aaRSs). aaRSs face enormous challenge in choosing the correct amino acid, wherein the differences are as small as a methyl group. As a result, aaRSs mischarge tRNAs with incorrect amino acid which is proofread by editing domains. Recently tRNA mis-selection was identified in kingdom Animalia, in which alanyl-tRNA synthetase (AlaRS) mischarges L-alanine on non-cognate tRNAThr containing G4●U69 (tRNA determinant of AlaRS is G3●U70), as a result L-Ala-tRNAThr is formed which may lead to mis-incorporations of alanine at threonine codons. Recently, a new proofreader which decouples these erroneously mischarged tRNAs, was identified and named as Animalia-specific tRNA deacylase (ATD). However, the physiological relevance of ATD is still unknown. My work involved checking the expression levels of ATD in different cell types using western blot analysis.

Keywords: proofreader, aminoacyl-tRNA synthetases, Animalia-specific tRNA deacylase

Errors are associated with every biological process. During translation, transfer RNAs (tRNAs) are charged with an amino acid and brought to the ribosome, where they are paired with the corresponding trinucleotide codon in messenger RNA (mRNA). The amino acid is transferred to the nascent polypeptide and the ribosome moves on to the next codon; the cycle repeats to produce a full-length polypeptide (Ibba M, Soll D., 1999). The overall translation error rate is about 10-3 and 10-4 (Jing L. et al., 2009). Fidelity of this process greatly depends on the pairing of cognate amino acid to its cognate tRNA. Such pairing is catalysed by a class of enzymes called aminoacyl-tRNA synthetases (aaRSs). AaRS’s are of two classes: class I and class II depending on their structure and amino acid activation chemistry. AaRSs define the genetic code by accurately pairing cognate tRNAs with their corresponding amino acids (Jing L. et al., 2009).

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