Abstract
Posttranscriptional modifications are critical for structure and function of tRNAs. Wybutosine (yW) and its derivatives are hyper-modified guanosines found at the position 37 of eukaryotic and archaeal tRNAPhe. TYW2 is an enzyme that catalyzes α-amino-α-carboxypropyl transfer activity at the third step of yW biogenesis. Using complementation of a ΔTYW2 strain, we demonstrate here that human TYW2 (hTYW2) is active in yeast and can synthesize the yW of yeast tRNAPhe. Structure-guided analysis identified several conserved residues in hTYW2 that interact with S-adenosyl-methionine (AdoMet), and mutation studies revealed that K225 and E265 are critical residues for the enzymatic activity. We previously reported that the human TYW2 is overexpressed in breast cancer. However, no difference in the tRNAPhe modification status was observed in either normal mouse tissue or a mouse tumor model that overexpresses Tyw2, indicating that hTYW2 may have a role in tumorigenesis unrelated to yW biogenesis.
Highlights
Though over 100 modified bases have been characterized in tRNAs, the biosynthetic pathways leading to many modifications in mammalian tRNAs are not well understood
Human TYW2 can substitute for the yeast enzyme in the biosynthesis of yW base in tRNAPhe Sequence analysis shows that the human TYW2 protein (448 amino acids) shares 35% identity with the yeast TYW2 protein (462 amino acids), and the homology primarily resides in its transferase domain
We have established that human TYW2 encodes the enzyme that is required for the posttranscriptional modification of the base G to yW in tRNAPhe (Figure 1)
Summary
Though over 100 modified bases have been characterized in tRNAs, the biosynthetic pathways leading to many modifications in mammalian tRNAs are not well understood. Wybutosine (yW) is one of the highly modified bases, located at position 37 in tRNAPhe, and its biosynthetic pathway, including characterization of four novel TYW enzymes (tRNA-yW synthesizing proteins), has been elucidated in yeast [1]. The biosynthesis of yW consists of a six-step process involving five different enzymes: TRM5, TYW1, TYW2, TYW3, TYW4 (Figure 1A) [1], and each step is mediated by the binding of S-adenosyl-methoinine (AdoMet). In the first step of the reaction, the G37 base of tRNAPhe is methylated by TRM5, a methyltransferase, using AdoMet as the methyl group donor. Step three is mediated by a transferase, TYW2, which transfers the bulky a-amino-a-carboxypropyl (acp) group from AdoMet to the side-chain at C-7 position of yW-187 to produce yW-86. We wanted to explore whether the human TYW2 provides a similar enzymatic activity to its yeast counterpart in yW biosynthesis
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
