The expression of tousled kinases in CaP cell lines and its relation to radiation response and DSB repair

Abstract

The Tousled-like kinases (TLKs) function in processes of chromatin assembly, including replication, transcription, repair, and chromosome segregation. TLK1/1B interacts specifically with the chromatin assembly factor Asf1, a histone H3-H4 chaperone, and with Rad9, a protein involved in DNA repair, and these interactions are believed to be responsible for the action of TLKs in double-strand break repair and radioprotection. Western blotting and RT-PCR were used to analyze the expression of TLK1, TLK1B, and TLK2 in a panel of prostate cancer (CaP) cell lines. The pattern of radiotolerance in the cell lines was analyzed in parallel. DU145 and PC-3 cells were also probed with assays utilizing transfected plasmids that could be cleaved in vivo with adeno-expressed HO nuclease to assess the potential contribution of TLK1/1B in DSB repair. This is the first report of TLKs' expression in a panel of CaP cell lines and their relationship to radioresistance. Furthermore, expression of TLK1B in non-expressing PC-3 cells rendered them highly resistant to radiation, and conversely, knockdown to TLK1/1B in expressing DU145 reduced their radiotolerance. TLKs appear to be intimately linked to the pattern of resistance to DNA damage, and specifically DSBs, a finding that was not reported before for any cell lines, and certainly not systematically for human prostate cell lines.