Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Saccharomyces cerevisiae, HOT1-stimulated recombination has been implicated in maintaining homology between repeated ribosomal RNA genes. The ability of HOT1 to stimulate genetic exchange requires RNA polymerase I transcription across the recombining sequences. The trans-acting nuclear mutation hrm3-1 specifically reduces HOT1-dependent recombination and prevents cell growth at 37 degrees . The HRM3 gene is identical to DEG1. Excisive, but not gene replacement, recombination is reduced in HOT1-adjacent sequences in deg1Delta mutants. Excisive recombination within the genomic rDNA repeats is also decreased. The hypo-recombination and temperature-sensitive phenotypes of deg1Delta mutants are recessive. Deletion of DEG1 did not affect the rate of transcription from HOT1 or rDNA suggesting that while transcription is necessary it is not sufficient for HOT1 activity. Pseudouridine synthase 3 (Pus3p), the DEG1 gene product, modifies the anticodon arm of transfer RNA at positions 38 and 39 by catalyzing the conversion of uridine to pseudouridine. Cells deficient in pseudouridine synthases encoded by PUS1, PUS2 or PUS4 displayed no recombination defects, indicating that Pus3p plays a specific role in HOT1 activity. Pus3p is unique in its ability to modulate frameshifting and readthrough events during translation, and this aspect of its activity may be responsible for HOT1 recombination phenotypes observed in deg1 mutants.
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PMID:DEG1, encoding the tRNA:pseudouridine synthase Pus3p, impacts HOT1-stimulated recombination in Saccharomyces cerevisiae. 1623 Nov 52

Pseudouridine, the so-called fifth nucleoside due to its ubiquitous presence in ribonucleic acids (RNAs), remains among the most challenging modified nucleosides to characterize. As an isomer of the major nucleoside uridine, pseudouridine cannot be detected by standard reverse-transcriptase-based DNA sequencing or RNase mapping approaches. Thus, over the past 15 years, investigators have focused on the unique structural properties of pseudouridine to develop selective derivatization or fragmentation strategies for its determination. While the N-cyclohexyl-N'-beta-(4-methylmorpholinium)ethylcarbodiimide p-tosylate (CMCT)-reverse transcriptase assay remains both a popular and powerful approach to screen for pseudouridine in larger RNAs, mass-spectrometry-based approaches are poised to play an increasingly important role in either confirming the findings of the CMCT-reverse transcriptase assay or in characterizing pseudouridine sequence placement and abundance in smaller RNAs. This review includes a brief discussion of pseudouridine including a summary of its biosynthesis and known importance within various RNAs. The review then focuses on chemical derivatization approaches that can be used to selectively modify pseudouridine to improve its detection, and the development of mass-spectrometry-based assays for the identification and sequencing of pseudouridine in various RNAs.
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PMID:Mass spectrometry of the fifth nucleoside: a review of the identification of pseudouridine in nucleic acids. 1862 Sep 15