SAP-like domain in nucleolar spindle associated protein mediates mitotic chromosome loading as well as interphase chromatin interaction

Journal Article · Fri Aug 12 04:00:00 EDT 2011 · Biochemical and Biophysical Research Communications

DOI:https://doi.org/10.1016/J.BBRC.2011.07.015· OSTI ID:22207439

Verbakel, Werner ^[1]; Carmeliet, Geert ^[2]; Engelborghs, Yves ^[1]

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1. Laboratory of Biomolecular Dynamics, Katholieke Universiteit Leuven, Celestijnenlaan 200G, Bus 2403, 3001 Heverlee (Belgium)
2. Laboratory of Experimental Medicine and Endocrinology, Katholieke Universiteit Leuven, Herestraat 49, Bus 902, 3000 Leuven (Belgium)

Highlights: {yields} The SAP-like domain in NuSAP is a functional DNA-binding domain with preference for dsDNA. {yields} This SAP-like domain is essential for chromosome loading during early mitosis. {yields} NuSAP is highly dynamic on mitotic chromatin, as evident from photobleaching experiments. {yields} The SAP-like domain also mediates NuSAP-chromatin interaction in interphase nucleoplasm. -- Abstract: Nucleolar spindle associated protein (NuSAP) is a microtubule-stabilizing protein that localizes to chromosome arms and chromosome-proximal microtubules during mitosis and to the nucleus, with enrichment in the nucleoli, during interphase. The critical function of NuSAP is underscored by the finding that its depletion in HeLa cells results in various mitotic defects. Moreover, NuSAP is found overexpressed in multiple cancers and its expression levels often correlate with the aggressiveness of cancer. Due to its localization on chromosome arms and combination of microtubule-stabilizing and DNA-binding properties, NuSAP takes a special place within the extensive group of spindle assembly factors. In this study, we identify a SAP-like domain that shows DNA binding in vitro with a preference for dsDNA. Deletion of the SAP-like domain abolishes chromosome arm binding of NuSAP during mitosis, but is not sufficient to abrogate its chromosome-proximal localization after anaphase onset. Fluorescence recovery after photobleaching experiments revealed the highly dynamic nature of this NuSAP-chromatin interaction during mitosis. In interphase cells, NuSAP also interacts with chromatin through its SAP-like domain, as evident from its enrichment on dense chromatin regions and intranuclear mobility, measured by fluorescence correlation spectroscopy. The obtained results are in agreement with a model where NuSAP dynamically stabilizes newly formed microtubules on mitotic chromosomes to enhance chromosome positioning without immobilizing these microtubules. Interphase NuSAP-chromatin interaction suggests additional functions for NuSAP, as recently identified for other nuclear spindle assembly factors with a role in gene expression or DNA damage response.

• OSTI ID: 22207439
• Journal Information: Biochemical and Biophysical Research Communications, Journal Name: Biochemical and Biophysical Research Communications Journal Issue: 4 Vol. 411; ISSN 0006-291X; ISSN BBRCA9
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
CHROMATIN
CHROMOSOMES
DNA
DNA DAMAGES
EPITHELIUM
FLUORESCENCE
GLUTATHIONE
GROWTH FACTORS
IN VITRO
MICROTUBULES
MITOSIS
NEOPLASMS
SPECTROSCOPY
VIRUSES