# Role of Phosphorylation in RNA Binding Protein Function

> **NIH NIH SC3** · CALIFORNIA STATE UNIVERSITY FULLERTON · 2021 · $106,500

## Abstract

Project Summary
Many RNA binding proteins (RBPs) that regulate alternative pre-mRNA splicing occur as gene families with
members sharing high primary and tertiary structural similarity. Yet these paralogs have non-overlapping tissue-
specific expression patterns and regulate over-lapping and distinct sets of target exons to elicit tissue-specific
splicing programs. How these paralogs achieve tissue-specific splicing patterns is not understood, and if known,
would facilitate the manipulation of gene expression to treat tissue-specific splicing related diseases. In this
project, we propose to investigate the role of post-translational phosphorylation in the tissue-specific splicing
activities of polypyrimidine tract binding proteins PTBP1 and PTPB2. The amino acid sequence of PTBP2 is 74%
identical to that of PTBP1. The two proteins share a similar domain organization, recognize and bind to the same
sequence elements in adjacent target exons and most often function as splicing repressors. However, PTBP1
and PTBP2 have distinct expression patterns that play a critical role in neuronal development and maturation.
Neuronal progenitor cells express PTBP1, but during differentiation the level of PTBP1 is down-regulated, and
that of PTBP2 is up-regulated. These changes in PTBP protein expression alter the splicing of a set of neuronal
exons leading to changes in many transcripts that code for proteins critical for development of axons, dendrites
and the formation of synapses. Thus, changes in PTPB1 and PTPB2 expression clearly alter (and thus regulate)
the patterns of splicing required for neuronal development. However, how these paralogs elicit these distinct
splicing outcomes is completely unknown. We recently discovered that PTBP1 and PTBP2 are post-
translationally phosphorylated under splicing conditions. PTBP2 has many more non-overlapping distinct sites
of phosphorylation than PTBP1 and these sites are localized to the unstructured N-terminal and linker regions,
which share less sequence identity than their RNA binding domains. Moreover, PTBP2 distinct phosphorylated
residues are not conserved in PTBP1, yet are maintained in lower species than humans implying they were
acquired/lost after gene duplication and that they may play a role in PTBP2 splicing activity. These findings
suggest that reversible phosphorylation might dictate the tissue-specific splicing activities of PTBP1 and PTBP2.
Our specific aims are to test this hypothesis.
Aim 1: Determine the role of phosphorylation in PTBP2 RNA binding activity
Aim 2: Determine the role of linker regions and phosphorylation in PTBP2 splicing regulation
Aim 3: Determine cell signaling pathways involved in PTBP2 neuronal splicing regulation
Our studies would answer fundamentally important questions about how structurally related paralogous proteins
dictate different splicing outcomes and also reveal how the neuronal splicing program is modulated via reversible
phosphorylation of RBPs such as PTPB2.
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## Key facts

- **NIH application ID:** 10134110
- **Project number:** 5SC3GM132036-03
- **Recipient organization:** CALIFORNIA STATE UNIVERSITY FULLERTON
- **Principal Investigator:** Niroshika a M Keppetipola
- **Activity code:** SC3 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $106,500
- **Award type:** 5
- **Project period:** 2019-04-01 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10134110

## Citation

> US National Institutes of Health, RePORTER application 10134110, Role of Phosphorylation in RNA Binding Protein Function (5SC3GM132036-03). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10134110. Licensed CC0.

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