# Role of a Novel Mitotic 4E-BP1 Protein Isoform in Cellular Transformation

> **NIH NIH R01** · UNIVERSITY OF PITTSBURGH AT PITTSBURGH · 2020 · $344,485

## Abstract

ABSTRACT
4E-BP1 is the primary gatekeeper for cancer cell, cap-dependent protein translation. It is directly targeted by the
mTOR pathway that is frequently dysregulated in cancer. We have found that CDK1/CYCB1 substitutes for
mTOR during mitosis to phosphorylate 4E-BP1 generating a novel phosphorylation mark at serine (S) 83 that is
not present when mTOR phosphorylates 4E-BP1. A mutant form of 4E-BP1 unable to be phosphorylated at S83
partially reverses cell transformation caused by the Merkel cell polyomavirus (MCV) small T oncoprotein. This
project is focused on investigating a novel CDK-1-dependent but mTOR-independent 4E-BP1 regulatory
pathway. The central hypothesis for this proposal is that S83 phosphorylation modulates translation of a unique
subset of mRNAs to facilitate mitosis-specific protein expression. In Aim I, substitution of a mutant (S83A) and
the phosphomimetic (S83D) 4EBP1 proteins into EIF4EBP1 null cells, as well as developing MEFs from the
EIF4EBP1 S83A knock-in mice will be used to assay the effects of S83 phosphorylation on basic cell
homeostasis, including cell cycle analysis, proliferation and protein synthesis. In Aim II, we will identify
differentially translated mRNAs as a result of mitotic 4E-BP1 phosphorylation through two complementary
approaches: ribosomal profiling of mitosis-arrested cells, and RNA immunoprecipitation and sequencing
(RIPseq). In Aim III we will use live-cell imaging tools to track and quantify dynamics of translation in live cells.
Finally in Aim IV, we will explore a unique knock-in mutant mouse model for 4E-BP1 dysregulation. Our studies
will advance our fundamental understanding of how a mitosis-specific hyperphosphorylated form of 4E-BP1
functions in normally cycling cells and how its dysregulation in cancer cells may contribute to human
malignancies.

## Key facts

- **NIH application ID:** 9879716
- **Project number:** 5R01CA232604-02
- **Recipient organization:** UNIVERSITY OF PITTSBURGH AT PITTSBURGH
- **Principal Investigator:** YUAN CHANG
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $344,485
- **Award type:** 5
- **Project period:** 2019-04-01 → 2024-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9879716

## Citation

> US National Institutes of Health, RePORTER application 9879716, Role of a Novel Mitotic 4E-BP1 Protein Isoform in Cellular Transformation (5R01CA232604-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9879716. Licensed CC0.

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