Transforming growth factor-beta-stimulated clone-22 is a member of a family of leucine zipper proteins that can homo- and heterodimerize and has transcriptional repressor activity.
TGF-beta-stimulated clone-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.
Kester
H A
HA
Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands.
Blanchetot
C
C
den Hertog
J
J
van der Saag
P T
PT
van der Burg
B
B
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D017124:Conserved Sequence; D019281:Dimerization; D019143:Evolution, Molecular; D005786:Gene Expression Regulation; D006801:Humans; D016350:Leucine Zippers; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014162:Transfection
D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C099726:TSC22D1 protein, human