tRNAHis maturation: an essential yeast protein catalyzes addition of a guanine nucleotide to the 5' end of tRNAHis.

Abstract

All tRNAHis molecules are unusual in having an extra 5' GMP residue (G(-1)) that, in eukaryotes, is added after transcription and RNase P cleavage. Incorporation of this G(-1) residue is a rare example of nucleotide addition occurring at an RNA 5' end in a normal phosphodiester linkage. We show here that the essential Saccharomyces cerevisiae ORF YGR024c (THG1) is responsible for this guanylyltransferase reaction. Thg1p was identified by survey of a genomic collection of yeast GST-ORF fusion proteins for addition of [alpha-32P]GTP to tRNAHis. End analysis confirms the presence of G(-1). Thg1p is required for tRNAHis guanylylation in vivo, because cells depleted of Thg1p lack G(-1) in their tRNAHis. His6-Thg1p purified from Escherichia coli catalyzes the guanylyltransferase step of G(-1) addition using a ppp-tRNAHis substrate, and appears to catalyze the activation step using p-tRNAHis and ATP. Thg1p is highlye conserved in eukaryotes, where G(-1) addition is necessary, and is not found in eubacteria, where G(-1) is genome-encoded. Thus, Thg1p is the first member of a new family of enzymes that can catalyze phosphodiester bond formation at the 5' end of RNAs, formally in a 3'-5' direction. Surprisingly, despite its varied activities, Thg1p contains no recognizable catalytic or functional domains.

• Authors: Weifeng Gu, Jane E Jackman, Amanda J Lohan, Michael W Gray, Eric M Phizicky
• Journal: Genes & development (Genes Dev) Vol. 17 Issue 23 Pg. 2889-901 (Dec 01 2003) ISSN: 0890-9369 [Print] United States
• PMID: 14633974 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• DNA Primers
• Guanine Nucleotides
• RNA, Transfer, His
• Saccharomyces cerevisiae Proteins
• Nucleotidyltransferases
• guanylyltransferase

Topics

• Amino Acid Sequence
• Base Sequence
• Catalysis
• DNA Primers
• Guanine Nucleotides (metabolism)
• Molecular Sequence Data
• Nucleotidyltransferases (chemistry, genetics, metabolism)
• Open Reading Frames
• RNA Processing, Post-Transcriptional
• RNA, Transfer, His (metabolism)
• Saccharomyces cerevisiae Proteins (metabolism)
• Sequence Homology, Amino Acid