DNA end-independent activation of DNA-PK mediated via association with the DNA-binding protein C1D

Abstract

DNA-dependent protein kinase (DNA-PK), which is involved in DNA double-strand break repair and V(D)J recombination, is comprised of a DNA-targeting component termed Ku and an ∼465-kD catalytic subunit, DNA-PK cs . Although DNA-PK phosphorylates proteins in the presence of DSBs or other discontinuities in the DNA double helix in vitro, the possibility exists that it is also activated in other circumstances via its association with additional proteins. Here, through use of the yeast two-hybrid screen, we discover that the recently identified high affinity DNA binding protein C1D interacts with the putative leucine zipper region of DNA-PK cs . Furthermore, we show that C1D can interact with DNA-PK in mammalian cells and that C1D is a very effective DNA-PK substrate in vitro. Finally, we establish that C1D directs the activation of DNA-PK in a manner that does not require DNA termini. Therefore, these studies provide a function for C1D and suggest novel mechanisms for DNA-PK activation in vivo.

The pyridinylfuranopyrimidine inhibitor, PI-103, chemosensitizes glioblastoma cells for apoptosis by inhibiting DNA repair

“…In nontransformed cells, DNA-PK is usually but not always (for example, Yavuzer et al, 1998) believed to be directly activated on a DSB (Pawelczak and Turchi, 2008), thereafter initiating the repair machinery while concurrently activating survival pathways, such as PI3K/Akt-mediated signaling (Bozulic et al, 2008), possibly by direct phosphorylation (Feng et al, 2004). In tumor cells, however, which are usually more dependent on PI3K-mediated survival signaling and frequently express stimuli-independent activity of this signaling cascade (Yuan and Cantley, 2008), the relationship between PI3K and DNA-PK can be altered.…”

ATM's leucine-rich domain and adjacent sequences are essential for ATM to regulate the DNA damage response

“…The predicted LZ in ATM is conserved between several mammalian species (Savitsky et al, 1995;Pecker et al, 1996), and in the ATM-related protein DNAPKcs (Yavuzer et al, 1998). The predicted LZ in ATM has an atypical structure, containing a proline between the third and fourth leucines of the repeat.…”

The role of ATM in DNA damage responses and cancer

“…The identity of proteins which may interact with the putative leucine zipper domain of ATM is unknown; however, both DNA-PK and ATR/FRP1 share such a region. In the case of DNA-PKcs, this domain was recently described to associate with high a nity to C1D, a DNA binding protein that is capable of activating the catalytic subunit of DNA-PK in addition to serving as a substrate for kinase activity in vitro (Yavuzer et al, 1998). Interestingly, C1D is also induced by DNA damage (Yavuzer et al, 1998).…”