# Mechanisms of Tubulin Dimer Regulatory Pathways and Their Impact on Microtubule Function

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA AT DAVIS · 2022 · $150,963

## Abstract

Project Summary
The dynamic microtubule cytoskeleton mediates intracellular organization, generates forces in dividing or
migrating eukaryotic cells, and forms tracks for intracellular trafficking. The fundamental properties of
microtubules, including polarized growth and “dynamic instability”, stem directly from the activities of the
microtubule building blocks, the α- and β-tubulin heterodimers. Three conserved tubulin cofactors and
dedicated Arf-like 2 G-protein form multi-subunit platforms for the biogenesis and degradation of αβ-tubulin
dimer, leading to a high concentration within the cytoplasm. The mechanisms for these assemblies remain
mostly mysterious, due in part to a lack of structural information. In addition, we do not understand how
conserved microtubule polymerases with arrays of Tumor Overexpressed Gene (TOG) domains recruit ab-
tubulins and accelerate their incorporation while tracking dynamic microtubule ends. Understanding these
cellular pathways is critical since genetic defects that impair either soluble ab-tubulin biogenesis or microtubule
polymerases are linked to inherited neurological and developmental disorders and are observed in human
cancers, respectively. This proposal explores the biochemical and physical mechanisms of ab-tubulin
biogenesis and microtubule polymerase assemblies and their impact on microtubule function. Our strategy
combines methods across multiple resolution scales, including in vitro reconstitution of purified protein
assemblies, structural studies by cryo-electron microscopy (cryo-EM), reconstitution of assemblies with
microtubule dynamics using in vitro fluorescence microscopy-based assays, and in vivo live imaging with
microtubules within living cells.
First, we will determine structural transitions describing ab-tubulin biogenesis assemblies and their functional
impact of αβ-tubulin biogenesis and degradation. During the previous period, we established reconstitution
system for these assemblies with ab-tubulin and describe cryo-EM structural studies leading to medium
resolution structures in complex with ab-tubulins. 1) We will determine structural states for the ab-tubulin
biogenesis assemblies in multiple biochemical states using high-resolution cryo-EM to understand how these
assemblies catalyze dimerization of ab-tubulin and its degradation. 2) We will dissect functional roles of
structural elements and interactions within current structures to determine their role in the ab-tubulin
biogenesis process using in vitro and in vivo methods. Second, we will examine the mechanisms of
microtubule polymerases with arrays of TOG domains their regulatory mechanisms. In the previous period, we
describe a new model for ab-tubulin recruitment and polymerization by TOG domain arrays as microtubule
polymerases, developed based on our structural and biochemical studies. We validated this model using in
vitro reconstitution and in vivo live imaging of structure-based designer defective mutants, revealing t...

## Key facts

- **NIH application ID:** 10625195
- **Project number:** 3R01GM110283-08S1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA AT DAVIS
- **Principal Investigator:** Jawdat MH Al-Bassam
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $150,963
- **Award type:** 3
- **Project period:** 2015-01-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10625195

## Citation

> US National Institutes of Health, RePORTER application 10625195, Mechanisms of Tubulin Dimer Regulatory Pathways and Their Impact on Microtubule Function (3R01GM110283-08S1). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10625195. Licensed CC0.

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