Phenotypes of Mutations in the 5′-UTR of a Limiting Transcription Factor in Aspergillus nidulans Can Be Accounted For by Translational Inhibition and Leaky Scanning

Abstract

The uaY gene encodes the transcriptional activator of purine catabolism genes in Aspergillus nidulans. uaY12 results in strongly defective growth on purines as nitrogen sources and in strongly diminished transcription of UaY-regulated genes. This mutation introduces an ATG codon 64 bp upstream of the uaY ATG, generating a 68-codon open reading frame (uORFA), overlapping with the uaY ORF. uaY12 revertants fall into three categories:i. The majority eliminate the aberrant ATG. The growth and transcriptional phenotypes of these revertants are identical to those of the wild type. ii. Two revertants create a stop codon in frame with the uaY12 aberrant ATG, shortening the length of the uORFA, thus uORFA no longer overlaps the uaY ORF. The latter are partial suppressors of the uaY12 mutation, while chain termination suppressors, in turn, suppress this novel phenotype. iii. Two partial suppressors are unlinked to uaY. These two mutations result in a pleiotropic phenotype usually associated with ribosomal proteins.We hypothesize that uORFA strongly diminishes translation of the uaY ORF and that revertants negate this effect by a number of different mechanisms. The first-AUG rule and the phenomena of translational inhibition and leaky scanning provide a coherent explanation of the results presented in this article.

Upstream AUG Codons in the Simian Immunodeficiency Virus SIVmac239 Genome Regulate Rev and Env Protein Translation

“…Similar regulatory scenarios have been described previously for HIV-1 Vpu and Env translation (1,35,38) (Fig. 8C) but also in other viruses and eukaryotes (34,40,44,50).…”

Mapping and Function Characterization of the Tomato Spotted wilt Virus Resistance Gene SlCHS3 in Solanum Lycopersicum

“…During gene transcription and translation, 5 -UTRs play important regulatory roles (Wilkie et al 2003) and participate in responses to environmental factors (Xiao et al 2014). Mutated sequences in 5 -UTRs may lead to transcriptional and translational abnormalities, which in turn alter the biological features of microorganisms or plants (Yan et al 2004;Oestreicher et al 2009;Hyodo et al 2017;Yang et al 2018). In this study, the SlCHS3 expression could in uence the content of avonoids, the reason of this may the exon, intron, and promoter sequences of SlCHS3 had mutations between the TSWV-resistant and -susceptible inbred lines.…”