PubMed · 11276244
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A J Lustig. 2001. Cdc13 subcomplexes regulate multiple telomere functions.. https://doi.org/10.1038/86157
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Information for the occurrence and extent of apoptosis in soft tissue sarcoma (STS) and their clinical implication are limited. In 102 cases of STSs, apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling method and expression of Bcl-2, Bax, MIB-1 and p53 protein was examined immunohistochemically. The apoptotic index of the STSs ranged from 0 to 15% with an average value of 1.9%. The mean values of positive cell staining for Bcl-2, Bax, MIB-1 and p53 protein were 32.1, 40.8, 17.0 and 20.3%, respectively. The extent of apoptosis and expression of Bcl-2 protein were correlated to the histologic types of the tumor. Synovial sarcoma had a significantly higher expression of Bcl-2 protein, and lower incidence of apoptosis. STS underwent apoptosis at a constitutional level. There were no significant relationships between extent of the apoptosis, expression of its regulatory proteins and prognosis of the patients.
In eukaryotic cells, DNA double-strand breaks can be repaired by non-homologous end-joining, a process dependent upon Ku70/80, XRCC4 and DNA ligase IV. In mammals, this process also requires DNA-PK(cs), the catalytic subunit of the DNA-dependent protein kinase DNA-PK. Previously, inositol hexakisphosphate (IP6) was shown to be bound by DNA-PK and to stimulate DNA-PK-dependent end-joining in vitro. Here, we localize IP6 binding to the Ku70/80 subunits of DNA- PK, and show that DNA-PK(cs) alone exhibits no detectable affinity for IP6. Moreover, proteolysis mapping of Ku70/80 in the presence and absence of IP6 indicates that binding alters the conformation of the Ku70/80 heterodimer. The yeast homologue of Ku70/80, yKu70/80, fails to bind IP6, indicating that the function of IP6 in non-homologous end-joining, like that of DNA-PK(cs), is unique to the mammalian end-joining process.
Splice variants of the Nmp4 gene include nuclear matrix transcription factors that regulate the type I collagen alpha1(I) polypeptide chain (COL1A1) promoter and several matrix metalloproteinase (MMP) genes. To date, these are the only Cys(2)His(2) zinc finger proteins known to bind within the minor groove of homopolymeric (dA.dT) DNA. Nmp4 isoforms contain from 5 to 8 Cys(2)His(2) zinc fingers, an SH3-binding domain that overlaps with a putative AT-hook and a polyglutamine-alanine repeat (poly(QA)). To determine the mechanistic significance of Cys(2)His(2) zinc finger association with this unusual consensus DNA binding element, we identified the Nmp4 DNA-binding and transcriptional activation domains. Zinc fingers 2, 3, and 6 mediated association with the homopolymeric (dA.dT) COL1A1/MMP DNA consensus element. The N terminus of the Nmp4 protein exhibited a strong trans-activation capacity when fused to the GAL4 DNA-binding domain, but this activity was masked within the context of the full-length Nmp4-GAL4 DNA-binding domain chimera. However, upon binding to the COL1A1/MMP homopolymeric (dA.dT) element, the native Nmp4 protein up-regulated transcription, and the poly(QA) domain acquired a significant role in trans-activation. We propose that allosteric effects induced upon zinc finger association with the homopolymeric (dA.dT) minor groove confer context-specific functionality to this unusual family of Cys(2)His(2) transcription factors.