Transforming Growth Factor-β-stimulated Clone-22 Is a Member of a Family of Leucine Zipper Proteins That Can Homo- and Heterodimerize and Has Transcriptional Repressor Activity

doi:10.1074/jbc.274.39.27439

Transforming Growth Factor-β-stimulated Clone-22 Is a Member of a Family of Leucine Zipper Proteins That Can Homo- and Heterodimerize and Has Transcriptional Repressor Activity*

From the Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands

Abstract

TGF-β-stimulatedclone-22 (TSC-22) encodes a leucine zipper-containing protein that is highly conserved during evolution. Two homologues are known that share a similar leucine zipper domain and another conserved domain (designated the TSC box). Only limited data are available on the function of TSC-22 and its homologues. TSC-22 is transcriptionally up-regulated by many different stimuli, including anti-cancer drugs and growth inhibitors, and recent data suggest that TSC-22 may play a suppressive role in tumorigenesis. In this paper we show that TSC-22 forms homodimers via its conserved leucine zipper domain. Using a yeast two-hybrid screen, we identified a TSC-22 homologue (THG-1) as heterodimeric partner. Furthermore, we report the presence of two more mammalian family members with highly conserved leucine zippers and TSC boxes. Interestingly, both TSC-22 and THG-1 have transcriptional repressor activity when fused to a heterologous DNA-binding domain. The repressor activity of TSC-22 appears sensitive for promoter architecture, but not for the histone deacetylase inhibitor trichostatin A. Mutational analysis showed that this repressor activity resides in the non-conserved regions of the protein and is enhanced by the conserved dimerization domain. Our results suggest that TSC-22 belongs to a family of leucine zipper-containing transcription factors that can homodimerize and heterodimerize with other family members and that at least two TSC-22 family members may be repressors of transcription.

Footnotes

↵* This work was supported by N. V. Organon, Oss, The Netherlands.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) .
↵‡ To whom correspondence should be addressed. Tel.: 31-30-2510211; Fax: 31-30-2516464; E-mail: bvdb@niob.knaw.nl.
↵2 H. A. Kester and B. van der Burg, unpublished observations.
↵4 The accession numbers of proteins are as follows: human TSC-22, Q15714; human DIP, NP004080; human KIAA0669, BAA31644; D. melanogaster shs, AAC41608; hypothetical protein from C. elegans (T18D3.7), Q22544; and chicken TSC-22, BAA11565.
↵5 H. A. Kester and B. van der Burg, unpublished observations.
↵3 H. A. Kester, C. E. van den Brink, P. T. van der Saag, and B. van der Burg, manuscript in preparation.
Abbreviations:

TSC-22

TGF-β-stimulated clone-22

TGF-β

transforming growth factor-β

shs

shortsighted

DIP

delta sleep inducing peptide

GST

glutathioneS-transferase

DBD

DNA-binding domain

HA tag

hemagglutinin tag

RD1 and RD2

repression domains 1 and 2

THG-1 and THG-2

TSC-22 homologous genes 1 and 2

EST

expressed sequence tag

4i5g

4×ICAM-5×GAL-TATA-luc reporter

4i5g-250

4×ICAM-5×GAL-250 bp-TATA-luc reporter

5g4i

5×GAL-4×ICAM-TATA-luc reporter

5g-250–4i

5×GAL-250 bp- 4×ICAM-TATA-luc reporter

RARα

retinoic acid receptor α

TSA

trichostatin A

gal-2h

fusion construct of the THG-1 fragment cloned in the yeast two-hybrid screen with the GAL-DBD

bp

base pair(s)

oligo

oligonucleotide

ICAM

intercellular adhesion molecule. GAL, DNA-binding site of yeast transcription factor GAL4

gal

DNA-binding domain of GAL4
- Received March 1, 1999.
- Revision received June 14, 1999.
The American Society for Biochemistry and Molecular Biology, Inc.