Molecular Mechanisms of eIF4E Mediated Transformation

Abstract
This revised renewal application investigates novel mechanisms driving dysregulation of post-
transcriptional control in cancer. Indeed, dysregulation of these events can drive the production
of proteins that underpin proliferation, survival, invasion and metastases. Dysregulation can
occur at many levels of RNA processing including splicing of RNAs, their nuclear export and
translation. The eukaryotic translation initiation factor eIF4E, dysregulated in ~30% of cancers
including in acute myeloid leukemia (AML), governs the RNA processing of networks of
transcripts that ultimately underpin its oncogenic activities. Its ability to govern these regulons
has been attributed to its well-established roles in nuclear export and translation of specific
RNAs. Here, we discovered that eIF4E reprograms the splicing landscape of 1000s of
transcripts both as a function of eIF4E dysregulation in AML patients as well as upon eIF4E
overexpression in model systems. We compared alternative splicing (AS) events in high-eIF4E
AML and upon eIF4E overexpression in cells, postulating those in common would represent
pan-cancer targets of eIF4E-dependent splicing. We discovered a set of ~150 AS “core”
transcripts, which encoded factors in the same biochemical networks. Importantly, these
pathways also play roles in AML and in cancer more generally. Many of the AS events are
predicted to produce proteins with different domain structures and thus altered functionalities.
As to the mechanisms by which eIF4E modulates AS, our studies unearthed physical
interactions between eIF4E and components of the spliceosome as well as revealed novel
means to control the production of the splicing machinery i.e. via eIF4E. Three aims are
proposed to dissect the mechanistic principles and biological impacts related to these novel
findings: Aim 1. Explore eIF4E-dependent alterations to splicing where we will dissect the
biochemical activities of eIF4E required for its AS activity, and assess the functional outcome of
this activity; Aim 2. Elucidate the biochemical role that eIF4E plays in re-programming splicing
by dissecting the physical interactions of eIF4E with components of the spliceosome and
ascertain its relationship with active spliceosomes; and Aim 3. Determine the impact of
dysregulated eIF4E-dependent splicing in AML where we will explore the impact of AS, and
identify the splicing factors required for eIF4E’s activity. These studies will transform our view
with regard to the impact of eIF4E dysregulation, which would now include altering the form of
the transcript as well as regulating its protein-coding capacity.

Grant Number: 5R01CA098571-21
NIH Institute/Center: NIH
Principal Investigator: KATHERINE BORDEN