# ESCRT and MIT Complexes in Cytokinesis

> **NIH NIH R01** · UTAH STATE HIGHER EDUCATION SYSTEM--UNIVERSITY OF UTAH · 2021 · $350,750

## Abstract

ABSTRACT
As cells exit mitosis, they pause at the abscission checkpoint to ensure that the mitotic program has been completed
successfully. They then proceed through abscission, irreversibly separating the two daughter cells. The Endosomal Sorting
Complexes Required for Transport (ESCRT) machinery plays essential roles in both of these important cytokinetic
processes. Certain ESCRT components are negatively regulated by the abscission checkpoint to prevent premature
abscission. Once the checkpoint is satisfied, the ESCRT machinery then assembles in the midbody to constrict the membrane
and carry out abscission. Projects in this proposal are designed to uncover the molecular mechanisms that underlie key steps
in these processes. Specifically, we will: characterize the regulation of ALIX, a key ESCRT factor that nucleates assembly
of constricting ESCRT-III filaments within the midbody (AIM 1), determine how ESCRT-III filaments recruit MIT domain-
containing proteins to the midbody and define how these proteins function in cytokinesis (AIM 2), and characterize the
structures and functions of the 9 related “meiotic clade” AAA ATPases that work together to promote abscission by
remodeling midbody microtubules and ESCRT-III filaments. Structural studies in Subaim 1.1 will target the different
conformational states along the ALIX activation pathway, with the goal of learning how mitotic phosphorylation activates
ALIX to participate in abscission. These studies will build on our previous biochemical and structural analyses of the ALIX
core domains, both free and in complex with ESCRT-III ligands. Cell biological studies in Subaim 1.2 will define how
checkpoint activation delays ALIX recruitment to the midbody and test whether ALIX sequestration inhibits abscission.
Preliminary studies have established the delay in ALIX recruitment and shown that checkpoint activation causes ALIX to
concentrate within cytoplasmic foci, together with other factors required for abscission and the abscission checkpoint. In
Subaim 2.1, we will identify and structurally characterize complexes of the 25 different human MIT domain proteins with
their binding sites on the tails of the 12 different ESCRT-III proteins. To date, these studies have revealed more than 20
new interactions and produced six structures of ESCRT-III-MIT complexes. Complementary studies in Subaim 2.2 will
identify human MIT proteins required for different stages of cytokinesis and characterize their functions. These approaches
have already identified three new MIT proteins with important roles in the abscission checkpoint. Structural studies in
Subaim 3.1 will target microtubule severing AAA ATPases in complex with relevant substrates. These studies will
complement our recent high resolution cryoEM structure of the related Vps4 AAA ATPase in complex with an ESCRT-III
substrate. Finally, biochemical studies in Subaim 3.2 will examine how these related enzymes discriminate between
ESCRT-III filaments and micr...

## Key facts

- **NIH application ID:** 10206169
- **Project number:** 5R01GM112080-07
- **Recipient organization:** UTAH STATE HIGHER EDUCATION SYSTEM--UNIVERSITY OF UTAH
- **Principal Investigator:** CHRISTOPHER P. HILL
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $350,750
- **Award type:** 5
- **Project period:** 2014-07-01 → 2023-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10206169

## Citation

> US National Institutes of Health, RePORTER application 10206169, ESCRT and MIT Complexes in Cytokinesis (5R01GM112080-07). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10206169. Licensed CC0.

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