Investigating the Role of Introns in Transcription‐Associated Mutagenesis in Budding Yeast

Abstract

A key feature required for cell survival is genomic stability, which is the ability of a cell to prevent mutations in its genome and repair them if they do occur. Genomic mutations can be generated in several ways, including transcription of a gene via transcription‐associated mutagenesis (TAM). Introns are known to be able to enhance transcription in vivo, but the influence of introns on TAM is not well‐understood. Here, our work investigates whether introns modulate the rate of TAM in a URA3 reporter gene using budding yeast as a model organism. Our preliminary results suggest that the presence of introns in the natively‐intronless URA3 gene is associated with elevated mutation rates of that gene. Interestingly, there appears to be an intron‐length‐dependent effect on this trend (i.e. the yeast strain with a long intron in the URA3 reporter demonstrated elevated URA3 gene mutation rates compared to the other two strains with either a short intron or no intron). Our findings suggest that the length and presence of introns in a gene are associated with increased mutagenesis of that gene. Furthermore, the long‐intron‐containing strains in our study grew slower in the absence of uracil than the short‐intron strains and no‐intron controls, possibly indicating an effect of intron length on splicing of the URA3 primary transcript. We are currently investigating if elevated transcription rate of a URA3 gene containing an intron causes an increase in TAM rate. In addition, URA3 reporter gene expression levels are being quantitated in each strain. We expect that URA3 mRNA transcript levels will be elevated in the intron‐containing URA3 yeast strains relative to those of the no‐intron controls. In future work for this study, we will determine the effect of the presence of an intron located near the promoter of an induced URA3 gene on the rate of TAM. Our future results will contribute to better understanding the impact of introns on the mutagenesis of highly‐expressed genes, which may play a role in mechanisms underlying mutagenesis in the human genome.Support or Funding InformationDr. Jane Kim’s research is supported by an NIH SCORE Grant (SC3GM127198).