Structural basis for the indispensable role of a unique zinc finger motif in LNX2 ubiquitination

LNX (Ligand of Numb Protein-X) proteins, LNX1 and LNX2, are RING- and PDZ-based E3-ubiquitin ligases known to interact with Numb. Silencing of LNX2 has been reported to down-regulate WNT and NOTCH, two key signaling pathways in tumorigenesis. Here we report the identification of the domain boundary...

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Main Authors:	Nayak, Digant, Sivaraman, J.
Format:	Online
Language:	English
Published:	Impact Journals LLC 2015
Online Access:	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4741457/

id	pubmed-4741457
recordtype	oai_dc
spelling	pubmed-47414572016-03-15 Structural basis for the indispensable role of a unique zinc finger motif in LNX2 ubiquitination Nayak, Digant Sivaraman, J. Research Paper LNX (Ligand of Numb Protein-X) proteins, LNX1 and LNX2, are RING- and PDZ-based E3-ubiquitin ligases known to interact with Numb. Silencing of LNX2 has been reported to down-regulate WNT and NOTCH, two key signaling pathways in tumorigenesis. Here we report the identification of the domain boundary of LNX2 to confer its ubiquitination activity, its crystal structure along with functional studies. We show that the RING domain in LNX2 is flanked by two Zinc-binding motifs (Zn-RING-Zn), in which the N-terminal Zinc-binding motif adopts novel conformation. Although this motif follows the typical Cys2His2-type zinc finger configuration, it is devoid of any secondary structure and forms an open circle conformation, which has not been reported yet. This unique N-terminal Zn-finger motif is indispensable for the activity and stability of LNX2, as verified using mutational studies. The Zn-RING-Zn domain of LNX2 is a dimer and assumes a rigid elongated structure that undergoes autoubiquitination and undergoes N-terminal polyubiquitination. The ubiquitin chains consist of all seven possible isopeptide linkages. These results were validated using full-length LNX2. Moreover we have demonstrated the ubiquitination of cell fate determinant protein, Numb by LNX2. Our study provides a structural basis for the functional machinery of LNX2 and thus provides the opportunity to investigate suitable drug targets against LNX2. Impact Journals LLC 2015-10-05 /pmc/articles/PMC4741457/ /pubmed/26451611 Text en Copyright: © 2015 Nayak & Sivaraman http://creativecommons.org/licenses/by/2.5/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
repository_type	Open Access Journal
institution_category	Foreign Institution
institution	US National Center for Biotechnology Information
building	NCBI PubMed
collection	Online Access
language	English
format	Online
author	Nayak, Digant Sivaraman, J.
spellingShingle	Nayak, Digant Sivaraman, J. Structural basis for the indispensable role of a unique zinc finger motif in LNX2 ubiquitination
author_facet	Nayak, Digant Sivaraman, J.
author_sort	Nayak, Digant
title	Structural basis for the indispensable role of a unique zinc finger motif in LNX2 ubiquitination
title_short	Structural basis for the indispensable role of a unique zinc finger motif in LNX2 ubiquitination
title_full	Structural basis for the indispensable role of a unique zinc finger motif in LNX2 ubiquitination
title_fullStr	Structural basis for the indispensable role of a unique zinc finger motif in LNX2 ubiquitination
title_full_unstemmed	Structural basis for the indispensable role of a unique zinc finger motif in LNX2 ubiquitination
title_sort	structural basis for the indispensable role of a unique zinc finger motif in lnx2 ubiquitination
description	LNX (Ligand of Numb Protein-X) proteins, LNX1 and LNX2, are RING- and PDZ-based E3-ubiquitin ligases known to interact with Numb. Silencing of LNX2 has been reported to down-regulate WNT and NOTCH, two key signaling pathways in tumorigenesis. Here we report the identification of the domain boundary of LNX2 to confer its ubiquitination activity, its crystal structure along with functional studies. We show that the RING domain in LNX2 is flanked by two Zinc-binding motifs (Zn-RING-Zn), in which the N-terminal Zinc-binding motif adopts novel conformation. Although this motif follows the typical Cys2His2-type zinc finger configuration, it is devoid of any secondary structure and forms an open circle conformation, which has not been reported yet. This unique N-terminal Zn-finger motif is indispensable for the activity and stability of LNX2, as verified using mutational studies. The Zn-RING-Zn domain of LNX2 is a dimer and assumes a rigid elongated structure that undergoes autoubiquitination and undergoes N-terminal polyubiquitination. The ubiquitin chains consist of all seven possible isopeptide linkages. These results were validated using full-length LNX2. Moreover we have demonstrated the ubiquitination of cell fate determinant protein, Numb by LNX2. Our study provides a structural basis for the functional machinery of LNX2 and thus provides the opportunity to investigate suitable drug targets against LNX2.
publisher	Impact Journals LLC
publishDate	2015
url	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4741457/
_version_	1613533732872912896

Structural basis for the indispensable role of a unique zinc finger motif in LNX2 ubiquitination

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