The carboxy-terminal hydrophobic domain of TIG3, a class II tumor suppressor protein, is required for appropriate cellular localization and optimal biological activity.
TIG3 is a recently discovered class II tumor suppressor protein, originally isolated from retinoid-treated cultured epidermal keratinocytes, that suppresses the proliferation of a variety of epithelial cell types. In the present study, we examine the ability of this protein to reduce CHO, T47D and HaCaT cell proliferation, and the role of the carboxy-terminal hydrophobic domain in this regulation. Vector-mediated expression of the full length TIG3 protein, TIG31-164, results in a 50-70% reduction colony formation efficiency. Expression of a truncated mutant, TIG31-134, that lacks the putative carboxy-terminal membrane-anchoring domain, results in a partial loss of ability to suppress colony formation. The fact that the truncated protein remains partially active suggests that both the amino- and carboxy-terminal regions of TIG3 are required for optimal growth suppression. The full-length protein is distributed in a perinuclear location, and is not present in the nucleus. TIG31-134, in contrast, is distributed in the cytoplasm. Thus, a change in location is associated with the partial loss of activity. We also monitored the distribution of green fluorescent protein (GFP)-TIG3 fusion proteins. GFP-TIG31-164 was localized in a pattern similar to that observed for TIG31-164, while GFP-TIG31-134 displayed a distribution pattern similar to GFP. This suggests that the c-terminal hydrophobic domain has an important role in determining the intracellular localization of TIG3. In addition, GFP-TIG31-164 retains the ability to inhibit cell function, while GFP-TIG31-134 is inactive.
Deucher
A
A
Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4970, USA.
Nagpal
S
S
Chandraratna
R A
RA
Di Sepio
D
D
Robinson
N A
NA
Dashti
S R
SR
Eckert
R L
RL
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D002455:Cell Division; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D018076:DNA, Complementary / Q000235:genetics; D016147:Genes, Tumor Suppressor; D051379:Mice; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000502:physiology; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051381:Rats; D018168:Receptors, Retinoic Acid; D011993:Recombinant Fusion Proteins / Q000502:physiology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D013347:Subcellular Fractions; D014162:Transfection; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
D002352:Carrier Proteins; D018076:DNA, Complementary; C437968:PLAAT4 protein, human; D010446:Peptide Fragments; D018168:Receptors, Retinoic Acid; D011993:Recombinant Fusion Proteins