Theses
Date of Award
2022
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Biological Sciences
First Advisor
Dr. Charles Query
Second Advisor
Dr. Kristina Ames
Third Advisor
Dr. Stephen Redenti
Fourth Advisor
Dr. Jack Henning
Abstract
The removal of introns from pre-messenger RNA via splicing in the nucleus is an essential step in gene expression. In recent decades, significant effort has been made to understand the chemical mechanisms of splicing reactions and the composition of the spliceosome that catalyzes them. Yet very little is known about the exact function of many splicing factors and small proteins within the spliceosome. Slu7, a pre-mRNA splicing factor, is essential during the second catalytic step of splicing because it interacts with several proteins and stabilizes the active site conformation. It has been found that Slu7 is involved in 3' splice site selection and may play a role in bringing the 3' splice site to the active site. It is found within the binding pocket of Prp8 and is a highly conserved nuclear protein. Recent EM density maps revealed that a small molecule, inositol hexakisphosphate (IP6), is found within the binding pocket of Prp8, close to the 5' exon and U5 snRNA loop. Our lab is testing mutants in the inositol polyphosphate biosynthesis pathway (IPP genes), including IP6, to determine the effect on splicing and if inositol polyphosphate (IPP) isoforms affect splicing outcomes. Close to the IP6 binding pocket, we can find Slu7. Slu7 contains a phylogenetically highly conserved RKDR motif among model organisms. We hypothesized that Slu7’s positively charged amino acids (arginine-R and lysine-K within the RKDR motif) are interacting with the negatively charged IPP molecules to stabilize the 5'exon /U5 snRNA during splicing. This study established that substituting mutations at the RKDR motif of SLU7 affects yeast growth and splicing efficiency. In yeast, alanine and glutamic acid mutations at the RKDR motif of SLU7 lead to cold and temperature sensitivity (a sick phenotype) and a lack of splicing efficiency, when mutations were introduced at the conserved intronic sites (5’SS, 3’SS, and the branch site) . These results suggest that a modification of the amino acids and charge composition present at the RKDR motif can modulate splicing by affecting the interactions between the 5' exon and U5 snRNA.
Recommended Citation
Chaudhry, Sovira A., "The role of SLU7 in spliceosome function in Saccharomyces cerevisiae" (2022). CUNY Academic Works.
https://academicworks.cuny.edu/le_etds/26