RESUMO
The hic-5 gene encodes a novel protein with Zn finger-like (LIM) motifs, the expression of which increases during cellular senescence. The ectopic expression of hic-5 in nontumorigenic immortalized human fibroblasts, whose expression levels of hic-5 were significantly reduced in comparison with those of mortal cells, decreased colony-forming efficiency. Stable clones expressing high levels of hic-5 mRNA showed higher levels of mRNAs for several extracellular matrix-related proteins, along with the alteration of an alternative splicing as seen in senescent cells and decreased c-fos inducibility. Furthermore, these clones acquired a senescence-like phenotype, such as growth retardation; senescence-like morphology; and increased expression of Cip1/WAF1/sdi1 after 20 to 40 population doublings. On the other hand, antisense RNA expression of hic-5 in human normal diploid fibroblasts delayed the senescence process. HIC-5 was localized in nuclei and had affinity for DNA. Based on these observations, we speculated that HIC-5 affected the expression of senescence-related genes through interacting with DNA and thereby induced the senescence-like phenotypes. To our knowledge, hic-5 is the first single gene that could induce senescence-like phenotypes in a certain type of immortalized human cell and mediate the normal process of senescence.
Assuntos
Proteínas do Citoesqueleto , Proteínas de Ligação a DNA/genética , Fibroblastos/citologia , Dedos de Zinco , Processamento Alternativo , Sequência de Aminoácidos , Animais , Divisão Celular , Linhagem Celular , Núcleo Celular/química , Senescência Celular/genética , Colagenases/genética , Inibidor de Quinase Dependente de Ciclina p21 , Ciclinas/genética , DNA/biossíntese , Proteínas de Ligação a DNA/análise , Fibronectinas/genética , Expressão Gênica , Genes fos/genética , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Proteínas com Domínio LIM , Camundongos , Dados de Sequência Molecular , Fenótipo , RNA Antissenso/genética , RNA Mensageiro/biossínteseRESUMO
TSC-36, a TGF beta1-inducible gene, encodes a polypeptide that shows significant similarity to SPARC (secreted protein rich in cysteine), and follistatin, an activin-binding protein. The expression of the TSC-36 gene was reported to be extinguished in v-ras-transformed mouse fibroblastic cells, and also was found also to be abrogated in cells transformed with v-myc. The level of expression was, however, not affected in cells transformed with v-src, v-abl, or v-raf. The TSC-36 cDNA was first isolated from mouse cells, and recently its rat and human homologues have been reported which show striking similarity with each other. In various human tumor cells, TSC-36 mRNA was almost undetectable. TSC-36 mRNA was detected in various mouse organs, but its level was the highest in the lung. TSC-36 mRNA level was the highest in the lung among mouse organs, and on in situ hybridization, the TSC-36 transcript was detected in the alveolar epithelium but not in the bronchial epithelium. These features suggest possible usage of TSC-36 as one of the markers in human tumors.
Assuntos
Regulação da Expressão Gênica , Genes ras , Glicoproteínas/metabolismo , Osteoblastos/metabolismo , Células 3T3 , Animais , Linhagem Celular , Linhagem Celular Transformada , Transformação Celular Viral , Proteínas Relacionadas à Folistatina , Humanos , Hibridização In Situ , Masculino , Camundongos , Camundongos Endogâmicos ICR , Proteínas Oncogênicas Virais/genética , RNA Mensageiro/metabolismo , Distribuição TecidualRESUMO
BACKGROUND: PAR-6, aPKC and PAR-3 are polarity proteins that co-operate in the establishment of cell polarity in Caenorhabditis elegans and Drosophila embryos. We have recently shown that mammalian aPKC is required for the formation of the epithelia-specific cell-cell junctional structure. We have also revealed that a mammalian PAR-6 forms a ternary complex with aPKC and ASIP/PAR-3, and localizes at the most apical end of the junctional complex in epithelial cells. RESULTS: The ternary complex formation and junctional co-localization of PAR-6 with aPKC and ASIP/PAR-3 are observed during the early stage of epithelial cell polarization. In addition, over-expression of the PAR-6 mutant with CRIB/PDZ domain in MDCK cells disturbs the cell-cell contact-induced junctional localization of tight junction proteins, as well as inhibiting TER development. Furthermore, the binding of Cdc42:GTP to the CRIB/PDZ domain of PAR-6 enhances the kinase activity of PAR-6-bound aPKC. Detailed analyses suggest that the binding of PAR-6 to aPKC has the intrinsic potential to activate aPKC, which is only released when Cdc42:GTP binds to the CRIB/PDZ domain. CONCLUSION: The results indicate the involvement of PAR-6 in the aPKC function which is required for the cell-cell adhesion-induced formation of epithelial junctional structures, possibly through the cooperative regulation of aPKC activity with Cdc42.