TLK1 Antibody #4125

Tousled-like kinases (TLK1 and TLK2) are nuclear serine/threonine kinases named for their homology to the Tousled gene from Arabidopsis thaliana, essential for flower development (1). The kinase activities of the TLKs are cell cycle regulated, with maximal activity during S phase (1). TLK appears to play a role in chromatin assembly and DNA damage checkpoint regulation (1,2). In C. elegans, TLK1 is essential for appropriate transcription during embryonic development (3). Substrates for TLK include the human chromatin assembly factor Asf, which functions in DNA replication- and repair-coupled chromatin assembly (2). DNA damage during S phase, when TLK is maximally active, leads to inhibition of TLK activity (1). This inhibition requires ataxia mutated kinase (ATM) and Chk1 (4,5). ATM and the related kinase ATR are activited by DNA damage during S phase, phosphorylate Chk1/Chk2, and block the transition into mitosis (6). Chk1 phosphorylates TLK1 on Ser743 in vitro and in vivo, leading to inhibition of TLK1 activity (4). This process likely provides a mechanism to slow the chromatin assembly processes controlled by TLK in the event of DNA damage.