Drosophila Enhancer of Rudimentary Homolog, ERH, Is a Binding Partner of RPS3, RPL19, and DDIT4, Suggesting a Mechanism for the Nuclear Localization of ERH.

Stuart I Tsubota,Anthony C Phillips

doi:10.1155/2016/8371819

Stuart I Tsubota, Anthony C Phillips

Open Access

https://doi.org/10.1155/2016/8371819

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Abstract

The protein enhancer of rudimentary homolog, ERH, is a small, highly conserved protein that has been found in animals, plants, and protists. Genetic and biochemical interactions have implicated ERH in the regulation of pyrimidine biosynthesis, DNA replication, transcription, mRNA splicing, cellular proliferation, tumorigenesis, and the Notch signaling pathway. In vertebrates and insects, ERH is nuclearly localized; however, an examination of the ERH amino-acid sequence does not reveal any nuclear localization signals. In this paper we show that the first 24 amino acids contain sequences necessary and sufficient for nuclear localization. Through yeast two-hybrid screens, three new binding partners of ERH, RPS3, RPL19, and DDIT4, were identified. RPS3 was isolated from both human and Drosophila screens. These interactions suggest functions of ERH in cell growth, cancer, and DNA repair. The ERH sequences necessary for the interactions between ERH and RPS3 and RPL19 are mapped onto the same 24-amino-acid region in ERH which are necessary for nuclear localization, suggesting that ERH is localizing to the nucleus through binding to one of its DNA-binding partners, such as RPS3 or RPL19.

Highlights

The Drosophila enhancer of rudimentary, e(r), gene encodes enhancer of rudimentary homolog (ERH), a small protein of 104 amino acids [1, 2]
To identify possible binding partners for Drosophila ERH, a yeast two-hybrid screen [15] was performed using Drosophila LexA-ERH as bait to screen a prey library consisting of Drosophila embryo cDNA clones fused to the transcription activation domain of Gal4
Five of the clones were of RPS3 and three of the clones were of RPL19

Summary

Introduction

The Drosophila enhancer of rudimentary, e(r), gene encodes enhancer of rudimentary homolog (ERH), a small protein of 104 amino acids [1, 2]. ERH is a highly conserved protein that has been found in plants, animals, and protists [2]. The vertebrate ERH homologues are very highly conserved. The human, mouse, and Xenopus proteins are identical and differ from the zebrafish ERH by a single conservative amino-acid change. The protein contains three α-helices and a β-sheet that fold into a novel threedimensional structure that comprises a single domain. Human ERH exists as a dimer and the dimerization occurs via binding between the β-sheets of the two monomers. The binding is accomplished through primarily seven highly conserved amino acids (Figure 1)

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