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

Ronald, Sharon; Sunavala‐Dossabhoy, Gulshan; Adams, Lisa K.; Williams, B. Jill; Benedetti, Arrigo De

doi:10.1002/pros.21358

Cited by 18 publications

(22 citation statements)

References 22 publications

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“…Silencing RNA-mediated suppression of TLKs eventually kills all cells (normal or cancer) even without IR or RMT. 11,30 These are essential proteins as chaperones, while the kinase activity seems less critical and needed for more complex and specialized functions, as shown here. In fact, we could produce a stable cell line of normal mammary fibroblasts expressing a TLK1-KD mutant (in the presence of wild-type endogenous TLKs), but we also used siRNA to complement the work, which arrested the cells and then killed them.…”

Section: Discussionmentioning

confidence: 59%

Phenothiazine Inhibitors of TLKs Affect Double-Strand Break Repair and DNA Damage Response Recovery and Potentiate Tumor Killing with Radiomimetic Therapy

et al. 2013

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The Tousled-like kinases (TLKs) are involved in chromatin assembly, DNA repair, and transcription. Two TLK genes exist in humans, and their expression is often dysregulated in cancer. TLKs phosphorylate Asf1 and Rad9, regulating double-strand break (DSB) repair and the DNA damage response (DDR). TLKs maintain genomic stability and are important therapeutic intervention targets. We identified specific inhibitors of TLKs from several compound libraries, some of which belong to the family of phenothiazine antipsychotics. The inhibitors prevented the TLK-mediated phosphorylation of Rad9(S328) and impaired checkpoint recovery and DSB repair. The inhibitor thioridazine (THD) potentiated tumor killing with chemotherapy and also had activity alone. Staining for γ-H2AX revealed few positive cells in untreated tumors, but large numbers in mice treated with low doxorubicin or THD alone, possibly the result of the accumulation of DSBs that are not promptly repaired as they may occur in the harsh tumor growth environment.

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Section: Discussionmentioning

confidence: 59%

Phenothiazine Inhibitors of TLKs Affect Double-Strand Break Repair and DNA Damage Response Recovery and Potentiate Tumor Killing with Radiomimetic Therapy

et al. 2013

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“…Improper regulation of this process caused by increased TLK activity (or deficient TLK inhibition) could promote cell survival after DNA damage, which in turn could lead to increased mutation rates, genomic instability and radioresistance. Several human cancers have been identified that feature mutations in the kinase domain of TLK1 [58–62], and high TLK1 expression levels correlate with radioresistance [63,64] thus raising the possibility that TLK1 is an oncogene and potential therapeutic target.…”

Section: Discussionmentioning

confidence: 99%

Tousled-Like Kinase-Dependent Phosphorylation of Rad9 Plays a Role in Cell Cycle Progression and G2/M Checkpoint Exit

Kelly

Davey

2013

PLoS ONE

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Genomic integrity is preserved by checkpoints, which act to delay cell cycle progression in the presence of DNA damage or replication stress. The heterotrimeric Rad9-Rad1-Hus1 (9-1-1) complex is a PCNA-like clamp that is loaded onto DNA at structures resulting from damage and is important for initiating and maintaining the checkpoint response. Rad9 possesses a C-terminal tail that is phosphorylated constitutively and in response to cell cycle position and DNA damage. Previous studies have identified tousled-like kinase 1 (TLK1) as a kinase that may modify Rad9. Here we show that Rad9 is phosphorylated in a TLK-dependent manner in vitro and in vivo, and that T355 within the C-terminal tail is the primary targeted residue. Phosphorylation of Rad9 at T355 is quickly reduced upon exposure to ionizing radiation before returning to baseline later in the damage response. We also show that TLK1 and Rad9 interact constitutively, and that this interaction is enhanced in chromatin-bound Rad9 at later stages of the damage response. Furthermore, we demonstrate via siRNA-mediated depletion that TLK1 is required for progression through S-phase in normally cycling cells, and that cells lacking TLK1 display a prolonged G2/M arrest upon exposure to ionizing radiation, a phenotype that is mimicked by over-expression of a Rad9-T355A mutant. Given that TLK1 has previously been shown to be transiently inactivated upon phosphorylation by Chk1 in response to DNA damage, we propose that TLK1 and Chk1 act in concert to modulate the phosphorylation status of Rad9, which in turn serves to regulate the DNA damage response.

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“…The fact that TLKs are overexpressed likely renders tumor cells more dependent on these kinases than normal tissues and, hence, their preferential TLK-targeted killing. In contrast to BCA, in the most common human CaP cell lines, only one or the other TLK gene is expressed [71], although typically at high level—we do not have the story yet for the analysis of patient samples. The significance of the TLK/Rad9 axis is perhaps even greater for prostate cancer for which several studies have implicated the critical role of Rad9 in disease progression and prognosis.…”

Section: Tlks In Man As Guardians Of Genome Stability and Their mentioning

confidence: 99%

The Tousled-Like Kinases as Guardians of Genome Integrity

Benedetti

2012

ISRN Molecular Biology

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The Tousled-like kinases (TLKs) function in processes of chromatin assembly, including replication, transcription, repair, and chromosome segregation. TLKs interact specifically (and phosphorylate) with the chromatin assembly factor Asf1, a histone H3-H4 chaperone, histone H3 itself at Ser10, and also Rad9, a key protein involved in DNA repair and cell cycle signaling following DNA damage. These interactions are believed to be responsible for the action of TLKs in double-stranded break repair and radioprotection and also in the propagation of the DNA damage response. Hence, I propose that TLKs play key roles in maintenance of genome integrity in many organisms of both kingdoms. In this paper, I highlight key issues of the known roles of these proteins, particularly in the context of DNA repair (IR and UV), their possible relevance to genome integrity and cancer development, and as possible targets for intervention in cancer management.

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

Abstract: 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.

Cited by 18 publications

References 22 publications

Phenothiazine Inhibitors of TLKs Affect Double-Strand Break Repair and DNA Damage Response Recovery and Potentiate Tumor Killing with Radiomimetic Therapy

Phenothiazine Inhibitors of TLKs Affect Double-Strand Break Repair and DNA Damage Response Recovery and Potentiate Tumor Killing with Radiomimetic Therapy

Tousled-Like Kinase-Dependent Phosphorylation of Rad9 Plays a Role in Cell Cycle Progression and G2/M Checkpoint Exit

The Tousled-Like Kinases as Guardians of Genome Integrity

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