# Mechanisms of Tubulin dimer Regulatory Pathways and their impact on Microtubule Function

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA AT DAVIS · 2020 · $17,204

## 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:** 10219718
- **Project number:** 3R01GM110283-06A1S1
- **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:** 2020
- **Award amount:** $17,204
- **Award type:** 3
- **Project period:** 2015-01-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10219718

## Citation

> US National Institutes of Health, RePORTER application 10219718, Mechanisms of Tubulin dimer Regulatory Pathways and their impact on Microtubule Function (3R01GM110283-06A1S1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10219718. Licensed CC0.

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