Intracellular redistribution of Ku immunoreactivity in response to cell-cell contact and growth modulating components in the medium.

Ku is a heterodimeric protein first recognized as a human autoantigen but now known to be widely distributed in mammalian cells. Analysis of repair-deficient mutant cells has shown that Ku is required for DNA repair, and roles in DNA replication and transcription have also been suggested on the basis of in vitro observations. Ku is generally regarded as a nuclear component.

Interacisternal A-particle (IAP) genes show similar patterns of hypomethylation in established and primary mouse plasmacytomas.

Alterations in cell programming associated with neoplastic transformation may involve widespread changes in patterns of DNA methylation. Increased expression of IAP elements in plasmacytomas compared with LPS-stimulated normal B-cells is accompanied by extensive hypomethylation of IAP sequences (Mietz and Kuff 1990), subsets of which are revealed with the LS2, LS3 and T1 probes. Multiple common LS- and PC-specific IAP loci are hypomethylated in established plasmacytomas, showing that hypomethylation does not occur entirely randomly.

DNA-dependent protein kinase is activated by nicks and larger single-stranded gaps.

DNA-PK is a DNA-activated serine/threonine protein kinase capable of phosphorylating a number of nuclear DNA-binding proteins. Purified human DNA-PK has two subunits, a 350-kDa polypeptide, Prkdc, which binds ATP and is presumed to contain the catalytic site, and the Ku autoantigen which mediates DNA binding and activation. Previous studies have shown that DNA-PK is activated in vitro by linear double-stranded DNA fragments; however, the Ku subunit binds a broader range of DNA structures.