The Binding of Ku Antigen to Homeodomain Proteins Promotes Their Phosphorylation by DNA-dependent Protein Kinase

Abstract

The Ku antigen (70-and 80-kDa subunits) is a regulatory subunit of DNA-dependent protein kinase (DNA-PK) that promotes the recruitment of the catalytic subunit of DNA-PK (DNA-PK cs ) to DNA ends and to specific DNA sequences from which the kinase is activated.

DNA-PK phosphorylation sites on Oct-1 promote cell survival following DNA damage

“…As shown previously (Schild-Poulter et al, 2001), the phosphorylation of Oct-1 by DNA-PK was dependent on the interaction of Ku with the homeodomain. Thus, addition of a neutral HOXC4 homeodomain to the N-terminus of Oct-1 replaced the Oct-1 homeodomain in promoting strong phosphorylation of the peptide (Figure 2d).…”

“…By contrast, Oct-1 with substitutions in cluster D (Oct-1 D) was up-regulated to levels similar to the WT protein. This suggested that Oct-1 stabilization following IR treatment was mediated by the cumulative effects of residues phosphorylated in Oct-1 regions A, B and C. Importantly, the interaction between Oct-1 and Ku (Schild-Poulter et al, 2001 was not affected by the amino-acid substitutions in Oct-1 mtABC (Figure 3c). …”

“…Initial work had indicated that one region of Oct-1 that could be efficiently phosphorylated by DNA-PK Modulation of cell survival through Oct-1 phosphorylation C Schild-Poulter et al in vitro was a peptide encoding aa 268 to aa 446, which encompassed the Oct-1 POU domain (Schild-Poulter et al, 2001. Tryptic analysis and sequencing revealed T276/S278, present at the edge of the POU domain, as the targets sites for DNA-PK in this region (Supplementary Figure 1).…”

“…In vitro experiments showed that the association of Oct-1 with Ku facilitated the phosphorylation of Oct-1 by DNA-PK (Schild-Poulter et al, 2001.…”

Systems analysis of the prostate tumor suppressor NKX3.1 supports roles in DNA repair and luminal cell differentiation

“…DNA-PK and PARP1 have important functions in DNA double strand break repair, recombination, and telomere maintenance but are also involved in chromatin and transcriptional control 36– 38 . For example, Ku proteins associate with a series of homeodomain proteins (HOXC4, OCT1, OCT2, DLX2) thereby recruiting them to DNA ends where they are phosphorylated by DNA-PK 39 . Such phosphorylation was proposed to lead to DNA damage-dependent changes in their transcriptional activities.…”