TLK1B promotes repair of UV-damaged DNA through chromatin remodeling by Asf1.
BACKGROUND
The mammalian protein kinase TLK1 is a homologue of Tousled, a gene involved in flower development in Arabidopsis thaliana. The function of TLK1 is not well known, although knockout of the gene in Drosophila, or expression of a dominant negative mutant in mouse mammary cells causes loss of nuclear divisions and chromosome mis-segregation. TLK1B is a splice variant of TLK1 and it confers radioresistance in a normal mammary mouse cell line possibly due to increased chromatin remodeling capacity, but the mechanism of resistance remains to be fully elucidated.


RESULTS
We now show that TLK1B also affords protection against UV radiation. We find that nuclear extracts isolated from TLK1B-containing mouse cells promote more efficient chromatin assembly than comparable extracts lacking TLK1B. TLK1B-containing extracts are also more efficient in repair of UV-damaged plasmid DNA assembled into nucleosomes. One of the two known substrates of TLK1 (or TLK1B) is the histone chaperone Asf1, and immuno-inactivation experiments suggest that TLK1B increases UV-repair through the action of Asf1 on chromatin assembly/disassembly.


CONCLUSIONS
Our studies provide evidence for TLK1B-mediated phosphorylation of Asf1 triggering DNA repair. We suggest that this occurs via Asf1-mediated chromatin assembly at the sites of UV damage.
Sen
Siddhartha P
SP
Department of Biochemistry and Molecular Biology and the Feist Weiller Cancer Center, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA. ssen@lsuhsc.edu
De Benedetti
Arrigo
A
D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D042002:Chromatin Assembly and Disassembly / Q000235:genetics / Q000502:physiology*; D004247:DNA / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair / Q000502:physiology*; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D018832:Molecular Chaperones; D009154:Mutation / Q000235:genetics; D009707:Nucleosomes / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D014466:Ultraviolet Rays
C491641:ASF1A protein, human; C491640:ASF1B protein, human; D018797:Cell Cycle Proteins; D006657:Histones; D018832:Molecular Chaperones; D009707:Nucleosomes; D004247:DNA; D017346:Protein Serine-Threonine Kinases; C425323:TLK1 protein, human