CCDC74A/B are K-fiber crosslinkers required for chromosomal alignment

Haining Zhou,Fulin Wang,Junlin Teng,Jianguo Chen,Qi Li,Xin Liang,Tianning Wang,Tao Zheng

doi:10.1186/s12915-019-0694-9

Haining Zhou, Fulin Wang + Show 6 more

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https://doi.org/10.1186/s12915-019-0694-9

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Abstract

BackgroundSpindle microtubule organization, regulated by microtubule-associated proteins, is critical for cell division. Proper organization of kinetochore fiber (K-fiber), connecting spindle poles and kinetochores, is a prerequisite for precise chromosomal alignment and faithful genetic material transmission. However, the mechanisms of K-fiber organization and dynamic maintenance are still not fully understood.ResultsWe reveal that two previously uncharacterized coiled-coil domain proteins CCDC74A and CCDC74B (CCDC74A/B) are spindle-localized proteins in mammalian cells. They bind directly to microtubules through two separate domains and bundle microtubules both in vivo and in vitro. These functions are required for K-fiber organization, bipolar spindle formation, and chromosomal alignment. Moreover, CCDC74A/B form homodimers in vivo, and their self-association activity is necessary for microtubule bundling and K-fiber formation.ConclusionsWe characterize CCDC74A and CCDC74B as microtubule-associated proteins that localize to spindles and are important K-fiber crosslinkers required for bipolar spindle formation and chromosome alignment.

Highlights

Spindle microtubule organization, regulated by microtubule-associated proteins, is critical for cell division
CCDC74A/B are spindle-localized proteins and required for chromosomal alignment To search new mitotic regulators, we picked up a number of functionally uncharacterized proteins with coiled-coil domains which were screened by centrosome mass spectrometry [20]
Immunostaining endogenous CCDC74A/B in COS-7 and HeLa cells confirmed that CCDC74A/B were localized at spindles and central spindles during mitosis (Fig. 1a, Additional file 1: Figure S1e)

Summary

Introduction

Spindle microtubule organization, regulated by microtubule-associated proteins, is critical for cell division. Proper organization of kinetochore fiber (K-fiber), connecting spindle poles and kinetochores, is a prerequisite for precise chromosomal alignment and faithful genetic material transmission. The mechanisms of K-fiber organization and dynamic maintenance are still not fully understood. The mitotic spindle, a microtubule-based machinery, is responsible for the proper chromosomal alignment and precise chromosomal segregation during cell division [1]. Kinetochore fibers (K-fibers), interpolar microtubules, and astral microtubules are the major components of mitotic spindle. K-fibers, parallel microtubule bundles, link chromosome to spindle pole and is crucial for chromosomal alignment and segregation [2]. A large number of regulators especially microtubule-associated proteins (MAPs) are implicated in the formation and stabilization of K-fiber structure [5].

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