Poster abstracts
Poster number 91 submitted by Dana Beseiso
Investigating Functional Changes in Transcription Start Site Usage in Breast Cancer
Dana Beseiso (Biological Chemistry, University of Michigan), Rachel Niederer, Ph.D. (Biological Chemistry, University of Michigan)
Abstract:
The expression of multiple messenger RNA (mRNA) isoforms from a single gene is essential for promoting cellular diversity and adapting to stress. Alternative Transcription Start Site (TSS) usage generates mRNAs with distinct 5′ ends and, consequently, distinct 5′ Untranslated Regions (5′ UTRs). Because 5′ UTRs contain regulatory elements that affect translational output, alternative TSS usage may provide an important mechanism for controlling protein abundance. However, it remains poorly understood whether this mechanism is broadly used, particularly during disease progression. We hypothesize that widespread changes in TSS usage alter the expression of 5′ UTR isoforms, thereby driving translational reprogramming and promoting cancer progression. To investigate 5′ UTR isoforms in high throughput, we performed Direct Analysis of Ribosome Targeting (DART) on a comprehensive set of annotated 5′ UTR isoforms using lysates generated from a well-established cell culture model of breast cancer progression. This model includes epithelial mammary MCF10A cells, well-differentiated malignant MCF10CA1h cells, and poorly differentiated malignant MCF10CA1a cells. DART reveals over 100-fold differences in ribosome recruitment between 5′ UTR isoforms of the same gene, with top-performing isoforms varying by lysate type. Additionally, we observe hundreds of isoforms that switch in their ribosome recruitment rank across lysates. Intriguingly, correlation in ribosome recruitment is higher between malignant lysates than between malignant and noncancer lysates, suggesting cancer-specific translational programs mediated by 5′ UTR isoforms. Our data suggest that distinct translational control elements may be optimized for different cellular and molecular environments. Identifying cancer-specific translational control elements in 5′ UTRs may inform novel anticancer therapeutic strategies.
Keywords: 5 UTR, Alternative TSSs, Translational Regulatory Elements