Tip60 Tumor Suppressor Requires Its NLS Motif to Interact with Importin &amp;lt;i&amp;gt;α&amp;lt;/i&amp;gt;

Eun Jeoung Lee,Sang Sun Kang,Sung Hwa Shin

doi:10.4236/cellbio.2019.81001

Abstract

Tip60 is a specific member of MYST (Moz-Ybf2/Sas3-Sas2-Tip60) family of nuclear histone acetyltransferases (HAT). It is essential for cellular survival, differentiation, and metabolism. A putative canonical NLS motif between the chromo domain and the zinc finger of Tip60 was identified. Here we show evidence that Tip60 is associated with importin α as its substrate and transported from cytoplasm to the nucleus. Pull down assay revealed that Tip60 was physically associated with importin α both in vivo and in vitro. Confocal microscopic observation showed that Tip60 and importin α were co-localized with each other. The localization of Tip60 to the nuclear and its interaction with importin α was disrupted when its putative NLS motif for binding to importin α was mutated (219RKRK222 &#8594 219AAAA222). However, attachment of this putative NLS motif to a cytoplasmic protein (YAP 1-210 fragment) promoted its nuclear localization. Based on transient transfection, Tip60 NLS motif mutant showed a substantial reduction in self-acetylation, HAT activity, and apoptotic ability whereas wild type Tip60 did not show such reduction. Taken together, our results demonstrate that importin α transports Tip60 from the cytoplasm to the nucleus through binding to the putative NLS motif of Tip60 for its tumor suppressing function.

Highlights

Results of the present study demonstrated that importin α could function as one Tip60 nuclear transporter
The putative Tip60 Nuclear Localization Sequences (NLS) is localized between chromodomain and Zn2+ finger based on site-directed mutagenesis analysis (Figure 1(A))
Our observation demonstrated that the interaction between Tip60 and importin α through NLS binding enhanced Tip60’s histone acetyltransferases (HAT) activity, and controlled its subcellular localization, our findings raised several questions regarding the interaction between Tip60 and importin α

Summary

Introduction

To elucidate its biological roles and identify proteins interacted with ectopically expressed Tip, the presence of associated ATPase and DNA helicase activities has been demonstrated [4] [5]. Functional experiments have revealed that Tip and its associated proteins play essential roles in DNA repair and apoptosis [6] [7]. Tip appears to be related to a variety of cellular functions depending on acetylation of its substrate proteins [4] [8] [9] [10]. Protein acetylation is a modification by acetyltransferases that catalyze the transfer of acetyl groups from acetyl coenzyme A to either ε-amino group of internal lysine residues or ε-amino group of N-terminal amino acids [11] [12]

Objectives

Methods

Results

Conclusion