Poster abstracts
Poster number 52 submitted by Jen Gallagher
When does splicing do more than remove introns?
Tulika Sharma (West Virginia University), Jen Gallagher (West Virginia University)
Abstract:
All organisms have evolved robust mechanisms for responding to changing cellular environments. Response to nutrient deprivation is coordinated by rapidly changing transcription and translation to quickly alter metabolic pathways to better equip the cells for changing nutrient conditions, and yet our understanding of how the molecular mechanisms that span across multiple processes remain obscure. Glyphosate, the active ingredient in the herbicide Roundup (GBH), inhibits aromatic amino synthesis, creating a starvation signal similar but distinct to exposure to rapamycin. From quantitative trait loci analysis in yeast differentially sensitive to GBH (both a lab and agricultural isolates), we identified variants in the MUD1 gene, which encodes a nonessential splicing factor in the U1 snRNP. Loss of no other non-essential U1 protein confers resistance to amino acid starvation while loss of TRAMP complex increases sensitivity to starvation. The TRAMP complex degrades polyA transcripts in the nucleus and starvation sensitivity is repressed by also knocking out Mud1. The most downregulated transcripts in starvation encode ribosomal protein genes (RPGs) and RPGs contain most of the introns in the S. cerevisiae genome. The spliceosome is limiting in the cell and one of the ways non-essential energy-intensive processes are regulated during starvation is by inefficient splicing. The splicing index for the transcriptome was calculated when yeast were starved with glyphosate, depleting nutrients in the cell. The U3 snoRNA is an intron-containing Box C/D snoRNA required for processing the pre-rRNA into the 18S rRNA of the small ribosomal subunit. There are two paralogs that are expressed at different levels and have many polymorphisms in the intron. Splicing of the minor allele (U3b) is reduced to a greater extent during starvation. The minor allele has numerous SNPs and it is unknown if U3b functions differently than the higher expressed major allele. Regulation of splicing during starvation allows cells to rapidly reallocate resources away from energy-intensive ribosome biogenesis when resources are limited.
Keywords: splicing, starvation, U3 snoRNA