HEXIM1/P-TEFb complex controls RNA polymerase II pause release and immediate early gene induction following neuronal
Myo Htet1, Camila Estay-Olmos1, Lan Hu2
1Molecular Pharmacology and Neuroscience, Loyola University Chicago Health Science Center, Maywood, Illinois, USA.
The Journal of Biological Chemistry
|February 27, 2026
Summary
Hexamethylene bisacetamide inducible 1 (HEXIM1) protein complexes regulate gene transcription in neurons. This study reveals HEXIM1
Area of Science:
- Neuroscience
- Molecular Biology
- Gene Regulation
Background:
- Cognitive functions, including memory, depend on new gene transcription in neurons.
- Immediate early genes (IEGs) are crucial for memory and are regulated by a paused RNA polymerase II (RNAP2) state.
- Positive transcription elongation factor b (P-TEFb) releases paused RNAP2, but its activity is modulated by inhibitors like Hexamethylene bisacetamide inducible 1 (HEXIM1).
Purpose of the Study:
- To investigate the role of HEXIM1 in neuronal gene transcription and its connection to cognitive processes.
- To explore the impact of HEXIM1-P-TEFb interactions on immediate early gene (IEG) induction.
- To understand how HEXIM1 influences the poised RNAP2 state in neurons.
Main Methods:
- Correlational analysis of HEXIM1 mRNA levels with cognitive impairment in Alzheimer's disease.
- Investigation of HEXIM1 and IEG induction in murine neuronal cultures following depolarization.
- Experimental modulation of P-TEFb activity via inhibition of its cyclin-dependent kinase 9 (CDK9) subunit.
Main Results:
- Neuronal HEXIM1 mRNA levels correlate with impaired cognition in Alzheimer's disease.
- HEXIM1 is induced in the hippocampus during memory formation and upon neuronal depolarization.
- Calcium influx releases P-TEFb from the HEXIM1 complex, and CDK9 inhibition affects IEG induction during repeated depolarization.
Conclusions:
- HEXIM1, in complex with P-TEFb, plays a critical role in establishing and resetting the poised RNAP2 state in neurons.
- This regulation is essential for the efficient activation of genes involved in synaptic plasticity and memory formation.
- Dysregulation of HEXIM1 may contribute to cognitive deficits observed in conditions like Alzheimer's disease.
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