ABSTRACT
The tumour suppressor p53 becomes activated as a transcription factor in response to DNA damage, but the mechanism for this activation is unclear. A good candidate for an upstream activator of p53 is the DNA-dependent protein kinase (DNA-PK) that depends on the presence of DNA breaks for its activity. Here we investigate the link between DNA damage and the activation of DNA-PK and of p53. To determine whether DNA-PK is an upstream mediator of the p53 DNA-damage response, we analysed a severe combined-immunodeficiency (SCID) mouse cell line, SCGR11, and the human glioma cell line M059J . Both cell lines lack any detectable DNA-PK activity. We find that p53 is incapable of binding to DNA in the absence of DNA-PK, that DNA-PK is necessary but not sufficient for activation of p53 sequence-specific DNA binding, and that this activation occurs in response to DNA damage. Our results establish DNA-PK as a link between DNA damage and p53 activation, and reveal the existence of a mammalian DNA-damage-response pathway.
Subject(s)
DNA Damage , DNA-Binding Proteins , Protein Serine-Threonine Kinases/metabolism , Tumor Suppressor Protein p53/metabolism , 3T3 Cells , Amino Acid Sequence , Animals , Cell Line , Cyclin-Dependent Kinase Inhibitor p21 , Cyclins/biosynthesis , Cyclins/genetics , DNA/metabolism , DNA-Activated Protein Kinase , Enzyme Activation , Enzyme Inhibitors , Humans , Mice , Mice, Inbred BALB C , Mice, SCID , Molecular Sequence Data , Nuclear Proteins , Protein Binding , Transcription, Genetic , Transcriptional Activation , Transfection , Tumor Cells, CulturedABSTRACT
The closing subtraction osteotomy of the first cuneiform effectively reduces pronounced obliquity of the first metatarsal cuneiform joint and predictably reduces the intermetatarsal angle in patients with metatarsus primus adductus. This osteotomy is combined with other procedures in surgical realignment of the first ray. Cases best suited for this procedure must be selected carefully. The procedure involves resecting the existing bone block from the opposing surfaces of the first and second metatarsal bases and from the distal one half of the opposing surfaces of the first and second cuneiforms. A triangular-shaped wedge of bone is then resected from the midbody of the first cuneiform while retaining a medial hinge. Closure of the first cuneiform osteotomy should require only minimal pressure. Two threaded Steinman pins transfix the osteotomy site. The vascular cancellous bone of the first cuneiform assures adequate healing of the osteotomy site.
