# Mechanisms of Plk1 at the mitotic centromere

> **NIH NIH R01** · UNIVERSITY OF WISCONSIN-MADISON · 2022 · $305,672

## Abstract

SUMMARY
Our goal is to identify how Polo-like kinase 1 (Plk1) signals at the human centromere to maintain genome
integrity. In mitosis, the kinetochore (KT) is assembled at the centromere and this complex is a major focus of
Plk1 activity. The KT is a 100 nm-structure assembled on the centromere that attaches chromosomes to the
mitotic spindle. Using super-resolution techniques, we have discovered that the bulk of Plk1 localizes to the
centromere, directly on chromatin >50 nm from the outer KT. Our long-term goal is to delineate Plk1 partners,
substrates, and timing of its activities to maintain faithful chromosome segregation. We are currently focused on
activities at the centromere, building on our key findings: Bloom Syndrome RecQ Helicase (BLM) directly or
indirectly mediates chromosome arm dislocation and centromere unwinding that occur with loss of Plk1 activity;
Plk1 regulates nascent transcripts on chromatin in mitosis and phosphorylates the N-terminus of Centromere
Protein C (CENP-C), both known to maintain KT integrity. Our central hypothesis is that a discrete centromere
pool of Plk1 stabilizes the mitotic centromere and operates through inactivating helicases, by supporting
transcription, and by maintaining CENP-C function. In Aim 1, we will map the spatial environments of Plk1 that
contribute to its functions along the KT-centromere axis. We will test the idea that a chromatin-localized pool of
Plk1 targets substrates and mediates activities separately from a KT-localized pool, to regulate faithful
chromosome segregation. Aim 2 will test how Plk1 dampens BLM helicase function to maintain centromere
integrity against mitotic pulling forces. To do this, we will identify Plk1 phosphorylation sites on the BLM protein,
determine the role of Plk1 on BLM localization, and evaluate how phosphorylation modulates its helicase
activities in biochemical assays and cells. Aim 3 will identify the role of Plk1 on CENP-C stabilization via direct
phosphorylation and transcriptional regulation. We have already mapped Plk1 phosphorylation sites on CENP-
C and have discovered that Plk1 regulates mitotic transcription. Towards this end, we will functionally analyze
the CENP-C phosphorylation events and identify the functional effect of Plk1 on RNA polymerases and mitotic
RNAs. Together, this work will reveal how Plk1 operates regionally in the KT to maintain genomic integrity.

## Key facts

- **NIH application ID:** 10381722
- **Project number:** 5R01GM141068-02
- **Recipient organization:** UNIVERSITY OF WISCONSIN-MADISON
- **Principal Investigator:** Mark E Burkard
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $305,672
- **Award type:** 5
- **Project period:** 2021-04-01 → 2025-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10381722

## Citation

> US National Institutes of Health, RePORTER application 10381722, Mechanisms of Plk1 at the mitotic centromere (5R01GM141068-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10381722. Licensed CC0.

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