Regulation of alternative splicing and its connections to cancer

This thesis presents two separate pieces of work pertaining to pre-mRNA splicing in mammalian cells. The first piece, as the main research project of the thesis, consists of two related parts. The first part identified the regulators of the alternative splicing of the PKM gene in cancer cells while the second part elucidates the molecular mechanism of how this mutually exclusive alternative splicing is regulated. The second piece investigates the molecular mechanism of how SRp38 functions as a splicing activator when phosphorylated. Cancer cells uniformly alter key aspects of their metabolism, including their glucose usage. In contrast to quiescent cells, which use most of their glucose for oxidative phosphorylation when oxygen is present, under the same conditions, most of the glucose consumed by cancer cells is converted to lactate. This phenomenon is known as aerobic glycolysis, and is critical for cancer cell growth. The pyruvate kinase isoform expressed by the cell is a key determinant of glucose usage.

Pyruvate kinase in most tissues is produced from the PKM gene, which is alternatively spliced to produce the PKM1 or PKM2 isoforms, which contain exons 9 or 10 respectively. Adult tissues, such as skeletal muscle and brain, express predominantly the PKM1 isoform, which is universally reverted to the embryonic PKM2 isoform in cancer cells. PKM2 expression promotes aerobic glycolysis. In Chapter 3, I describe a mechanism by which cancer cells promote switching to PKM2.