Poster abstracts
Poster number 72 submitted by Whitney Jimenez
Distal elements in the MDM2 gene facilitate an eight-exon splicing event by coordinating multiple splice regulatory proteins
Whitney D. Jimenez (The Ohio State University College of Medicine, Biomedical Sciences), Zac LaRocca-Stravalle (Abigail Wexner Research Institute at Nationwide Childrens Hospital), Aishwarya G. Jacob (University of Cambridge), Ravi K. Singh (University of Houston), Dawn S. Chandler (The Ohio State University )
Abstract:
Alternative splicing is a key post-transcriptional mechanism that diversifies biological processes. Recent advances in high-throughput sequencing have uncovered many alternatively spliced variants involved in tumorigenesis, highlighting the role of splicing regulation in cancer. Our lab focuses on MDM2-Alt1, a spliced variant of the oncogene MDM2, a negative regulator of the tumor suppressor p53. In response to cancer or genotoxic stress, MDM2 undergoes alternative splicing to form MDM2-Alt1, consisting of exons 3 and 12. This variant is upregulated in tumors such as breast, lung, and rhabdomyosarcomas (RMS), but little is known about the regulators of its splicing. We hypothesize that MDM2-Alt1 splicing is driven by trans factors and cis elements on exons 4 and 11 of MDM2 pre-mRNA, orchestrating an 8-exon splice event.
Using RNA affinity chromatography and mass spectrometry, we identified several trans factors binding cis elements on intron 11 under damaged conditions. Notably, RNA-binding proteins FUBP1, MATR3, and PTBP1 were confirmed to interact with intron 11 of the MDM2 minigene. Our lab demonstrated that FUBP1 and PTBP1 positively regulate MDM2 splicing, while MATR3 promotes MDM2-Alt1 formation. Chimeric minigene experiments also highlighted exons 4 and 11 as critical for the damage response. We identified cis elements in intron 11 and exon 11 and the trans factors governing MDM2 splicing. FUBP1 and PTBP1 support canonical splicing, while MATR3 drives the formation of MDM2-Alt1. This work emphasizes the importance of exons 4 and 11 in genotoxic stress response and elucidates the dynamic interaction between cis elements and trans factors. Our findings advance the understanding of MDM2 alternative splicing and its regulatory balance. This research opens avenues for targeting alternative splicing in cancer therapy, with potential therapeutic strategies aimed at modulating MDM2-Alt1 splicing in tumors where it is implicated.
Keywords: MDM2, Splicing, RNA-Binding Proteins