Leucine zipper structure of TSC-22 (TGF-beta stimulated clone-22) markedly inhibits the anchorage-independent growth of salivary gland cancer cells.
Several investigators have demonstrated that TGF-beta stimulated clone-22 (TSC-22) regulates cell growth and differentiation, and cell death. TSC-22 is a putative transcriptional regulator containing a leucine zipper-like structure and a nuclear export signal. We previously showed the cytoplasmic localization of TSC-22 and the nuclear translocation of TSC-22 concomitant with induction of apoptosis in salivary gland cancer cells. In the present study, we attempted to identify the active domain of TSC-22 protein that regulated the biological functions of TSC-22. We constructed three mammalian expression vectors, which could produce full length TSC-22 only in cytoplasm, the leucine zipper structure of TSC-22 in both cytoplasm and nucleus, and the leucine zipper structure only in nucleus. Then, we transfected a salivary gland cancer cell line, HSG with these expression vectors, and investigated the growth profile of the transfectants. None of the TSC-22 constructs inhibited the monolayer growth and the anchorage-dependent colony formation of HSG cells. However, the leucine zipper structure of TSC-22 markedly inhibited the anchorage-independent colony formation of HSG cells (p<0.001; one way ANOVA). Full length TSC-22 also suppressed the anchorage-independent colony formation of HSG cells, although the effect of full length TSC-22 was much lower than those of the leucine zipper constructs. These observations suggest that the leucine zipper structure in TSC-22 protein is an active domain that negatively regulates the growth of salivary gland cancer cells.
Hino
Satoshi
S
Second Department of Oral and Maxillofacial Surgery, Tokushima University School of Dentistry, Tokushima 770-8504, Japan.
Kawamata
Hitoshi
H
Omotehara
Fumie
F
Uchida
Daisuke
D
Begum
Nasima-Mila
NM
Yoshida
Hideo
H
Sato
Mitsunobu
M
Fujimori
Takahiro
T
D020816:Amino Acid Motifs / Q000502:physiology; D002448:Cell Adhesion / Q000187:drug effects; D003114:Colony-Forming Units Assay; D017931:DNA Primers; D049452:Green Fluorescent Proteins; D006801:Humans; D016350:Leucine Zippers / Q000502:physiology*; D008164:Luminescent Proteins / Q000235:genetics; D019913:Nuclear Localization Signals / Q000502:physiology; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000502:physiology*; D012468:Salivary Gland Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000628:therapy; D014162:Transfection; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D008164:Luminescent Proteins; D019913:Nuclear Localization Signals; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C099726:TSC22D1 protein, human; D049452:Green Fluorescent Proteins