Date of Graduation

5-2025

Degree Type

Dissertation/Thesis

Degree Name

Bachelor of Science (BS)

Major

Biological Science

Advisor(s)

Berish Rubin

Second Advisor

Sylvia Anderson

Abstract

Although the human genome has a limited number of genes, alternative splicing allows the production of thousands of proteins. Alternative splicing is a regulated mechanism in which a messenger RNA (mRNA) synthesizes different proteins called isoforms, variants of the same protein that may have different cellular functions [1]. The unspliced sequence, also known as the primary transcript, results from the transcription of a genetic sequence by RNA Polymerase II, which produces an mRNA containing introns (non-coding regions) and exons (coding regions) [2]. The splicing process is catalyzed by the spliceosome, a ribonucleoprotein mega-particle composed of small nuclear ribonucleoproteins (snRNPs), U1, U2, U4, U5, U6, and other auxiliary factors (U2AF65 and U2AF35) [2]. The spliceosome recognizes the introns’ 5’ and 3’ splice sites and performs the two transesterification reactions necessary to cleave the introns and link the exons [2]. Those splice sites are classified as either ‘strong’ or ‘weak’ depending on how much they differ from the consensus sequence [3]. ‘Strong’ splice sites get recognized more often by the spliceosome, resulting in constitutive splicing [3]. In contrast, ‘weak’ splice sites are not consistently recognized by the spliceosome, giving rise to mRNA variants through alternative splicing [3]. The position of ‘weak’ and ‘strong’ sites influences how the spliceosome assembles and, consequently, what type of alternative splicing takes place; these include: inclusion of alternative mutually exclusive cassette exons and alternative cassette exons, alternative 5’ or 3’ splice sites, and alternative intron retention [2]. Alternative splicing is mainly regulated by cis-regulatory sequences, which include exonic splicing enhancers and silencers (ESEs and ESSs) and intronic splicing enhancers and silencers (ISEs and ISSs) [2-3]. Similarly,

3

trans-splicing factors such as serine/arginine-rich (SR) proteins and hnRNPs (heterogeneous nuclear ribonucleoprotein) can promote or inhibit splicing [2-3]. Evidence has shown that more than 95% of human genes experience alternative splicing, making the above-explained mechanisms and regulations essential for organismal complexity and protein functions [4]. Of the approximately 20,000 human protein-coding genes, 37% produce isoforms, contributing to the protein diversity [5]. Other RNA-sequencing studies revealed the participation of alternative splicing in gene regulation, cell differentiation, and tissue and organ development [5]. Nonetheless, its importance also comes with complications; mutations on the genetic code can lead to abnormal splicing (or mis-splicing) of the transcribed mRNA, resulting in non-functional or harmful proteins, but more importantly, genetic diseases [5].

Download

Share

COinS