Tài liệu Báo cáo khoa học: An autoinhibitory effect of the homothorax domain of Meis2 ppt

An autoinhibitory effect of the homothorax domain of

Meis2

Cathy Hyman-Walsh, Glen A. Bjerke and David Wotton

Department of Biochemistry and Molecular Genetics, and Center for Cell Signaling, University of Virginia, Charlottesville, VA, USA

Introduction

Homeodomain (HD) proteins were first identified in

flies, and are conserved across diverse species from

yeasts to mammals [1,2]. The characteristic DNA-bind￾ing HD is 60 amino acids in length and consists of

three a-helices [3]. It is the third a-helix within the HD

that is the primary DNA-binding region, although

there are other DNA contacts outside helix 3 [4–7]. In

addition to binding DNA, the HD is a protein interac￾tion module that mediates interactions with other

DNA-binding proteins and non-DNA-binding tran￾Keywords

homeodomain; Meis; Pbx; repression;

transcription

Correspondence

D. Wotton, Center for Cell Signaling,

University of Virginia, Box 800577, HSC,

Charlottesville, VA 22908, USA

Fax: +1 434 924 1236

Tel: +1 434 243 6752

E-mail: [email protected]

(Received 16 December 2009, revised 24

March 2010, accepted 30 March 2010)

doi:10.1111/j.1742-4658.2010.07668.x

Myeloid ecotropic insertion site (Meis)2 is a homeodomain protein contain￾ing a conserved homothorax (Hth) domain that is present in all Meis and

Prep family proteins and in the Drosophila Hth protein. The Hth domain

mediates interaction with Pbx homeodomain proteins, allowing for efficient

DNA binding. Here we show that, like Meis1, Meis2 has a strong C-termi￾nal transcriptional activation domain, which is required for full activation

of transcription by homeodomain protein complexes composed of Meis2

and Pbx1. We also show that the activity of the activation domain is inhib￾ited by the Hth domain, and that this autoinhibition can be partially

relieved by the interaction of Pbx1 with the Hth domain of Meis2. Target￾ing of the Hth domain to DNA suggests that it is not a portable trans￾acting repression domain. However, the Hth domain can inhibit a linked

activation domain, and this inhibition is not limited to the Meis2 activation

domain. Database searching reveals that the Meis3.2 splice variant, which

is found in several vertebrate species, disrupts the Hth domain by removing

17 codons from the 5¢-end of exon 6. We show that the equivalent deletion

in Meis2 derepresses the C-terminal activation domain and weakens inter￾action with Pbx1. This work suggests that the transcriptional activity of all

members of the Meis⁄ Prep Hth protein family is subject to autoinhibition

by their Hth domains, and that the Meis3.2 splice variant encodes a

protein that bypasses this autoinhibitory effect.

Structured digital abstract

l MINT-7718353, MINT-7718083, MINT-7718172, MINT-7718256, MINT-7718300, MINT￾7718330: Meis2d (uniprotkb:O14770-4) physically interacts (MI:0915) with PBX1 (uniprotkb:

P40424) by anti tag coimmunoprecipitation (MI:0007)

l MINT-7718110: Meis2e (uniprotkb:O14770-5) physically interacts (MI:0915) with PBX1

(uniprotkb:P40424) by anti tag coimmunoprecipitation (MI:0007)

Abbreviations

AD, activation domain; EST, expressed sequence tag; GBD, Gal4 DNA-binding domain; HD, homeodomain; hr1, homology region 1;

hr2, homology region 2; Hth, homothorax; HTH, Hth protein; Meis, myeloid ecotropic insertion site; SV40, simian virus 40.

2584 FEBS Journal 277 (2010) 2584–2597 ª 2010 The Authors Journal compilation ª 2010 FEBS