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

BACKGROUND 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. METHODS 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. RESULTS 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. CONCLUSIONS 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. Prostate 71:1367–1373, 2011. © 2011 Wiley‐Liss, Inc.