# The essential role of cyclin-dependent kinase CRK9 in trypanosome pre-mRNA processing

> **NIH NIH R01** · UNIVERSITY OF CONNECTICUT SCH OF MED/DNT · 2021 · $410,000

## Abstract

Summary
 The kinetoplastid parasites Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp. affect millions
of people worldwide, causing Human African Trypanosomiasis (HAT), Chagas’ disease, and various forms of
Leishmaniasis, respectively. Since drugs for these neglected tropical diseases are limited, often toxic and difficult
to administer, and parasite resistance to existing drugs is on the rise, it is important to develop new chemo-
therapeutic strategies. Our research is focused on trypanosome gene expression because the underlying
mechanisms deviate substantially from those in the human host. For example, polycistronic transcription of
protein coding genes and processing of pre-mRNA by spliced leader trans splicing are parasite-specific steps in
mRNA synthesis and maturation. We discovered in T. brucei that the activity of the cyclin-dependent kinase
(CDK) CRK9 is required for trans splicing. By generating a cell line that expresses analog-sensitive CRK9 and
no wild-type enzyme, we could chemically inhibit the enzyme in specific manner in cultured cells. Surprisingly,
we observed an instant splicing block after applying the inhibitor, suggesting that CRK9 carries out essential
reversible phosphorylation on the RNA processing machinery. Our preliminary data indicate that one of CRK9’s
substrate is the SR protein and known splicing factor TSR1, and that blocking CRK9 activity affects the assembly
of the spliceosome, the large and dynamic RNA-protein complex that carries out the splicing reaction.
Consequently, we will determine the mechanism of how CRK9 aids or controls the splicing process. Furthermore,
CDKs represent a highly druggable enzyme class, and CRK9 forms an unusual trimeric enzyme complex with a
deviant L-type cyclin and a kinetoplastid-specific protein, suggesting that CRK9 is a promising target for
chemotherapeutic intervention. Therefore, we propose to characterize the enzyme complex and determine a
minimal complex that is active and can be expressed recombinantly as prerequisite for future high throughput
inhibitor screens. Finally, based on preliminary data, we will test the hypothesis that CRK9 is the target of the
compound SCYX-7158 which is currently in clinical trials against HAT.

## Key facts

- **NIH application ID:** 10219576
- **Project number:** 1R01AI150919-01A1
- **Recipient organization:** UNIVERSITY OF CONNECTICUT SCH OF MED/DNT
- **Principal Investigator:** ARTHUR GUNZL
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $410,000
- **Award type:** 1
- **Project period:** 2021-03-02 → 2026-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10219576

## Citation

> US National Institutes of Health, RePORTER application 10219576, The essential role of cyclin-dependent kinase CRK9 in trypanosome pre-mRNA processing (1R01AI150919-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10219576. Licensed CC0.

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