Affinage

TLK1

Serine/threonine-protein kinase tousled-like 1 · UniProt Q9UKI8

Length
766 aa
Mass
86.7 kDa
Annotated
2026-04-28
35 papers in source corpus 16 papers cited in narrative 16 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

TLK1 is a nuclear serine/threonine kinase that coordinates chromatin assembly, DNA damage repair, cell cycle checkpoint signaling, and mitotic fidelity through phosphorylation of a diverse substrate repertoire. It phosphorylates histone H3 to regulate chromosome condensation and segregation (PMID:14583098), Rad9 (S328) and RAD54 (T41/T59/T700) to modulate the 9-1-1 checkpoint complex and homologous recombination repair (PMID:18940270, PMID:37439356), NEK1 (T141) to activate the ATR–Chk1 DNA damage response cascade and maintain mitochondrial integrity via VDAC1 (PMID:30737777, PMID:31914854), and MK5 (S354) to drive cancer cell motility (PMID:35064619). TLK1 is itself inactivated by Chk1-mediated phosphorylation following DNA damage or replication stress (PMID:20581459), and its recruitment to damaged chromatin requires a PCNA-interacting PIP box whose accessibility is negatively regulated by dimerization-dependent N-terminal hyper-autophosphorylation (PMID:39727191). A TLK1 kinase-impairing variant (p.Q479E) is associated with a neurodevelopmental disorder characterized by elevated spontaneous DNA damage and altered cytokine responses (PMID:38868186).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 1997 Medium

    Establishing that TLK1 is a serine/threonine kinase with intrinsic nuclear localization resolved its subcellular context and set the stage for identifying nuclear substrates.

    Evidence GST-fusion nuclear localization assay and COS-1 cell transfection

    PMID:9427565

    Open questions at the time
    • Kinase substrates unknown
    • Cellular function uncharacterized
    • Only a single cell line tested
  2. 2003 High

    Demonstrating that TLK1 phosphorylates histone H3 and that its loss causes chromosome condensation defects, missegregation, and S-phase arrest linked TLK1 to chromatin regulation and cell cycle progression.

    Evidence Kinase-dead dominant negative, siRNA knockdown, FACS, and immunofluorescence in breast epithelial cells

    PMID:14583098

    Open questions at the time
    • Whether H3 phosphorylation is direct or via an intermediary kinase was not fully resolved
    • Mechanism connecting TLK1 to S-phase arrest unclear
  3. 2005 Medium

    Identification of p68 RNA helicase (DDX5) as a TLK1 substrate, with phosphorylation reducing RNA binding, extended TLK1's reach beyond chromatin to RNA metabolism.

    Evidence In vitro kinase assay with recombinant TLK1, gel shift assay, TLK1 overexpression in HT1080 cells

    PMID:15950181

    Open questions at the time
    • Phosphorylation site on p68 not mapped
    • In vivo functional consequence of reduced RNA binding unknown
  4. 2008 High

    Two parallel discoveries established TLK1 as a DNA damage repair factor: it phosphorylates Rad9-S328 to modulate 9-1-1 complex occupancy at DSBs and facilitates chromatin reassembly even independently of kinase activity, while also regulating mitotic chromosome segregation through MRLC phosphorylation.

    Evidence HO endonuclease DSB system with ChIP and chromatin assembly assays (Rad9); RNAi with phosphomimetic DD-MRLC rescue (MRLC)

    PMID:18838128 PMID:18940270

    Open questions at the time
    • Kinase-independent chromatin assembly mechanism unresolved
    • Whether Rad9 and MRLC phosphorylation are coordinated during the cell cycle unknown
    • Asf1 vs Rad9 competition for TLK1 binding not structurally explained
  5. 2010 Medium

    Placing TLK1 downstream of Chk1 as a target inactivated upon DNA damage/hypoxia established TLK1 as a damage-sensitive kinase whose activity is switched off during replication stress.

    Evidence Cell-based assays under hypoxia with Chk1 loss-of-function and phosphorylation analysis

    PMID:20581459

    Open questions at the time
    • Precise Chk1 phosphorylation site(s) on TLK1 not fully mapped
    • Kinetics of TLK1 reactivation after damage resolution unknown
  6. 2019 High

    Discovery that TLK1 phosphorylates NEK1 at T141 and that this feeds into the ATR–Chk1 DDR pathway created a coherent signaling axis (TLK1→NEK1→ATR→Chk1) relevant to therapy resistance in prostate cancer.

    Evidence In vitro phosphorylation, NEK1-T141A mutant xenografts, tissue microarray, thioridazine TLK1 inhibitor, TRAMP mouse model

    PMID:30737777 PMID:30928383

    Open questions at the time
    • Whether TLK1 directly phosphorylates ATR or acts solely through NEK1 not resolved
    • Selectivity of thioridazine as a TLK1 probe limited
  7. 2020 Medium

    Connecting TLK1→NEK1 to VDAC1 phosphorylation and mitochondrial integrity broadened TLK1's role beyond the nucleus to include apoptosis resistance at the mitochondrial level.

    Evidence NEK1-T141A mutant overexpression, doxorubicin, oxygen consumption measurement, cytochrome C fractionation

    PMID:31914854

    Open questions at the time
    • TLK1's contribution inferred indirectly through NEK1-T141A; direct TLK1 perturbation not shown for mitochondrial phenotypes
    • VDAC1 phosphorylation site by NEK1 not mapped
  8. 2021 Medium

    Identifying AKTIP as a TLK1 substrate (T22/S237) that enhances AKT-PDK1 association linked TLK1 to the PI3K/AKT survival pathway, providing a mechanistic explanation for TLK1's role in cancer cell survival beyond DDR.

    Evidence Co-IP, in vitro phosphorylation, AKTIP knockdown, phospho-western blot, TLK1 inhibitor J54

    PMID:35366279

    Open questions at the time
    • AKTIP phosphorylation sites confirmed only in vitro; in vivo phospho-site verification lacking
    • Relative contribution of TLK1-AKTIP vs TLK1-NEK1 axes to cell survival not dissected
  9. 2022 High

    Demonstration that TLK1 directly activates MK5 via S354 phosphorylation to drive cancer cell motility established a kinase cascade (TLK1→MK5) governing migration and invasion independent of the DDR axis.

    Evidence In vitro kinase assay, MK5-S354A mutagenesis, MK5-null MEF rescue, 2D/3D motility assays

    PMID:35064619

    Open questions at the time
    • Downstream effectors of MK5 mediating cytoskeletal remodeling not identified
    • Whether TLK1→MK5 operates in non-cancer contexts unknown
  10. 2023 High

    Mapping three TLK1 phosphorylation sites on RAD54 (T41, T59, T700) with opposing effects on homologous recombination repair revealed how TLK1 fine-tunes HR pathway output.

    Evidence ISce-I HR reporter, in vitro kinase assay, site-directed mutagenesis, Co-IP with RAD51

    PMID:37439356

    Open questions at the time
    • Structural basis of opposing effects of N-terminal vs C-terminal RAD54 phosphorylation unknown
    • Temporal regulation of differential phosphorylation during HR not established
  11. 2024 High

    Three advances in 2024 resolved how TLK1 reaches damage sites (via a PIP box masked by dimerization-dependent autophosphorylation), linked the TLK1→NEK1 axis to YAP nuclear retention and transcriptional activation, and associated a kinase-impaired TLK1 variant with a neurodevelopmental disorder.

    Evidence PIP-box mutagenesis with laser micro-irradiation and live-cell imaging (recruitment); ChIP and YAP-Y407F mutagenesis (YAP); patient-derived lymphoblasts with comet assay and RNA-seq (disease variant)

    PMID:38868186 PMID:39199688 PMID:39727191

    Open questions at the time
    • Structural basis of PIP-box masking by autophosphorylation not determined at atomic resolution
    • NEK1-mediated Y407 phosphorylation on YAP is indirect from TLK1—direct kinase for Y407 not identified
    • Single patient with Q479E variant; replication in additional families needed

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include the structural mechanism of TLK1 dimerization-dependent autophosphorylation and PIP-box regulation, the identity and regulation of TLK1 activating kinases, whether the multiple TLK1 substrate axes (NEK1, RAD54, MK5, AKTIP, H3, Rad9) are coordinated in a unified signaling logic, and the full spectrum of TLK1 loss-of-function phenotypes in human development.
  • No high-resolution structure of TLK1 or TLK1 dimer
  • Upstream activating kinase for TLK1 not identified
  • Relative contribution of TLK1 vs TLK2 to each substrate axis not systematically dissected

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 6
Localization
GO:0005634 nucleus 3
Pathway
R-HSA-73894 DNA Repair 4 R-HSA-162582 Signal Transduction 2 R-HSA-1640170 Cell Cycle 2 R-HSA-4839726 Chromatin organization 2 R-HSA-5357801 Programmed Cell Death 1

Evidence

Reading pass · 16 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1997 TLK1 (PKU-beta) is a serine/threonine protein kinase that localizes to the nucleus via an N-terminal nuclear localization signal; the NLS-containing GST-fusion was shown to localize to the nucleus in transfection experiments, and PKU-beta expressed in COS-1 cells was predominantly nuclear. Biochemical cloning, GST-fusion nuclear localization assay, transient transfection in COS-1 cells Gene Medium 9427565
2003 TLK1 phosphorylates histone H3 in vitro and in vivo; expression of a kinase-dead TLK1B dominant negative mutant reduced phosphorylated histone H3 levels, caused chromosome condensation defects, chromosome missegregation, and aneuploidy in normal diploid breast epithelial cells. siRNA-mediated TLK1 depletion caused S-phase cell cycle block. Kinase-dead dominant negative overexpression, FACS, immunofluorescence microscopy, siRNA knockdown BMC cell biology High 14583098
2005 TLK1 phosphorylates the DEAD-box RNA helicase p68 (DDX5); in vitro kinase assay showed phosphorylation of the p68 C-terminal fragment by recombinant TLK1, and overexpression of TLK1 in HT1080 cells increased phosphorylation of endogenous p68. Phosphorylation of the p68 C-terminal fragment by TLK1 reduced its affinity for single-stranded RNA. In vitro kinase assay, gel shift assay, TLK1 overexpression in HT1080 cells, immunoprecipitation Biochemical and biophysical research communications Medium 15950181
2008 TLK1B binds Rad9 (component of the 9-1-1 complex) and phosphorylates hRad9 at S328; TLK1B overexpression hastened repair of DSBs, modulated 9-1-1 complex occupancy at DSBs, and stimulated chromatin reassembly adjacent to a DSB independently of kinase activity (kinase-dead TLK1B also stimulated chromatin assembly), suggesting a chaperone-like function. Rad9 and Asf1 compete for binding to TLK1B. Co-immunoprecipitation, in vitro kinase assay, S328A mutagenesis, HO endonuclease-induced DSB, chromatin assembly assay, chromatin immunoprecipitation DNA repair High 18940270
2008 TLK1 (PKU-beta) depletion by RNAi caused reduced phosphorylation of myosin II regulatory light chain (MRLC) at Ser19/Thr18 and resulted in unequal chromosome segregation; expression of phosphomimetic DD-MRLC rescued chromosome segregation defects, indicating TLK1 regulates mitosis via MRLC phosphorylation. RNAi knockdown, immunoblot, immunofluorescence, rescue with DD-MRLC expression Mutation research Medium 18838128
2010 In response to severe hypoxia, Chk1 is activated and phosphorylates TLK1, leading to its inactivation; this places TLK1 downstream of Chk1 in the DNA damage response pathway triggered by hypoxia-induced replication arrest. Cell-based assays under hypoxia, Chk1 loss-of-function, phosphorylation analysis Cell cycle (Georgetown, Tex.) Medium 20581459
2019 TLK1B is upregulated following androgen deprivation therapy (ADT) and acts upstream of NEK1 and ATR to mediate the DNA damage response (DDR) in prostate cancer cells; the pathway ADT > TLK1 > NEK1 > ATR > Chk1 was established by showing that TLK1 inhibition with thioridazine impairs ATR and Chk1 activation and leads to apoptosis. TLK1 inhibitor (thioridazine) treatment, phosphorylation western blot, clonogenic survival assay, LNCaP xenografts, genetic NEK1-T141A mutant International journal of cancer High 30737777
2019 TLK1 phosphorylates NEK1 at T141 to activate it; p-Nek1-T141 is elevated in prostate cancer biopsies correlating with Gleason score, and the TLK1-Nek1 axis is a common adaptive response during androgen-insensitive progression. In vitro phosphorylation, NEK1-T141A mutant xenografts, tissue microarray with pNek1-T141 antibody, TRAMP mouse model with TLK1 inhibitor Cancer letters High 30928383
2020 TLK1 activates NEK1 via T141 phosphorylation, and this TLK1/NEK1 axis contributes to VDAC1 phosphorylation and stability, thereby maintaining mitochondrial permeability and integrity; cells overexpressing NEK1-T141A showed increased apoptosis, cytochrome C leakage, and altered mitochondrial metabolism upon DNA damage. NEK1-T141A mutant overexpression, doxorubicin treatment, oxygen consumption measurement, cytochrome C fractionation, cell cycle analysis Cell cycle (Georgetown, Tex.) Medium 31914854
2020 In vitro kinase assays confirmed TLK1 inhibitory activity of the phenothiazine analog J54; J54 impairs the TLK1>NEK1>ATR>Chk1 DDR pathway and mediates apoptosis in prostate cancer cells and LNCaP xenografts. In vitro kinase assay, molecular docking, cell viability assays, xenograft model iScience Medium 32905878
2021 TLK1 interacts with and phosphorylates AKTIP at T22 and S237; TLK1-mediated AKTIP phosphorylation enhances AKT association with PDK1 and promotes AKT phosphorylation at T308 and S473, connecting TLK1 to the PI3K/AKT survival pathway in prostate cancer. Interactome analysis, Co-IP, in vitro phosphorylation, AKTIP knockdown, phospho-western blot, TLK1 inhibitor J54 Pathophysiology Medium 35366279
2022 TLK1 directly phosphorylates MK5 (MAPK-activated protein kinase 5) at S160, S354, and S386, resulting in MK5 activation; TLK1-mediated phosphorylation of MK5-S354 is required for prostate cancer cell motility, as MK5-S354A expression in MK5-null MEFs failed to rescue motility. This TLK1>MK5 axis drives PCa cell migration and invasion. In vitro kinase assay, phospho-specific antisera (pMK5-S354), Co-IP in HEK293 cells, MK5 knockout MEF rescue, 2D/3D motility assays, TLK1/MK5 KO and KD, TMA immunohistochemistry Molecular oncology High 35064619
2023 TLK1 phosphorylates RAD54 at T41, T59 (N-terminal domain) and T700 (C-terminal domain); phosphorylation at T41 and T59 supports homologous recombination repair (HRR) and protects cells from DSB damage, while phosphorylation at T700 impairs HRR and reveals a new RAD54-CTD interaction with RAD51. ISce-I-GR-DsRed HRR reporter assay, TLK1 inhibition/depletion, site-directed mutagenesis, in vitro kinase assay, cytotoxicity assays, Co-IP with RAD51 Nucleic acids research High 37439356
2024 TLK1 and TLK2 are hyper-autophosphorylated at their N-termini via homo- or hetero-dimerization; this hyper-autophosphorylation masks a conserved non-canonical PIP box and suppresses recruitment of TLK1/2 to damaged chromatin. Mutation of the PIP box abolishes recruitment to DNA damage sites, establishing that TLK1 associates with PCNA through its PIP box to reach damage sites. Autophosphorylation assay, PIP-box mutagenesis, laser micro-irradiation/live-cell imaging at damage sites, dimerization analysis, biochemical fractionation Nucleic acids research High 39727191
2024 TLK1 (via NEK1) promotes nuclear retention and transcriptional activation of YAP through stabilizing phosphorylation at Y407; pYAP-Y407 shows stronger association with co-activators AR and TEAD1 and ChIP confirms YAP-wt but not YAP-Y407F occupancy at ARE- and TEAD1-driven gene promoters. TLK1 inhibitor J54 reverses YAP nuclear retention and dephosphorylates Y407. ChIP, nuclear/cytoplasmic fractionation, co-immunoprecipitation with AR/TEAD1, GFP-YAP-Y407F mutagenesis, TLK1 inhibitor J54 treatment, LNCaP and VCaP xenografts Cancers Medium 39199688
2024 A TLK1 variant (p.Q479E) associated with a neurodevelopmental disorder impairs kinase activity but does not strongly alter TLK1 localization or proximal protein interactions; cells expressing this variant showed elevated spontaneous DNA damage and reduced cytokine responses, indicating TLK1 kinase activity is required for genomic and immune homeostasis. Patient-derived lymphoblast cell lines, single-cell gel electrophoresis (comet assay), western blot for DNA damage markers, flow cytometry, RNA-seq, biochemical kinase activity assay iScience Medium 38868186

Source papers

Stage 0 corpus · 35 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2019 Circular RNA TLK1 Aggravates Neuronal Injury and Neurological Deficits after Ischemic Stroke via miR-335-3p/TIPARP. The Journal of neuroscience : the official journal of the Society for Neuroscience 177 31311824
2008 Tousled homolog, TLK1, binds and phosphorylates Rad9; TLK1 acts as a molecular chaperone in DNA repair. DNA repair 63 18940270
2020 The circular RNA TLK1 exacerbates myocardial ischemia/reperfusion injury via targeting miR-214/RIPK1 through TNF signaling pathway. Free radical biology & medicine 57 32445866
2003 The C. elegans Tousled-like kinase (TLK-1) has an essential role in transcription. Current biology : CB 56 14614817
2021 Circular RNA TLK1 Promotes Sepsis-Associated Acute Kidney Injury by Regulating Inflammation and Oxidative Stress Through miR-106a-5p/HMGB1 Axis. Frontiers in molecular biosciences 51 34250012
2003 A dominant negative mutant of TLK1 causes chromosome missegregation and aneuploidy in normal breast epithelial cells. BMC cell biology 42 14583098
2019 Targeting the TLK1/NEK1 DDR axis with Thioridazine suppresses outgrowth of androgen independent prostate tumors. International journal of cancer 40 30737777
2019 The TLK1-Nek1 axis promotes prostate cancer progression. Cancer letters 36 30928383
2020 The TLK1/Nek1 axis contributes to mitochondrial integrity and apoptosis prevention via phosphorylation of VDAC1. Cell cycle (Georgetown, Tex.) 35 31914854
2020 Generation of Phenothiazine with Potent Anti-TLK1 Activity for Prostate Cancer Therapy. iScience 30 32905878
2023 TLK1-mediated RAD54 phosphorylation spatio-temporally regulates Homologous Recombination Repair. Nucleic acids research 23 37439356
2010 Exposure to acute hypoxia induces a transient DNA damage response which includes Chk1 and TLK1. Cell cycle (Georgetown, Tex.) 20 20581459
2008 PKU-beta/TLK1 regulates myosin II activities, and is required for accurate equaled chromosome segregation. Mutation research 14 18838128
2022 TLK1-mediated MK5-S354 phosphorylation drives prostate cancer cell motility and may signify distinct pathologies. Molecular oncology 11 35064619
2022 Circular RNA TLK1 Exerts Oncogenic Functions in Hepatocellular Carcinoma by Acting as a ceRNA of miR-138-5p. Journal of oncology 11 35359342
1997 cDNA cloning and chromosomal mapping of genes encoding novel protein kinases termed PKU-alpha and PKU-beta, which have nuclear localization signal. Gene 11 9427565
2021 Inhibiting of circ-TLK1 inhibits the progression of glioma through down-regulating PANX1 via targeting miR-17-5p. Journal of molecular histology 10 34181173
2022 The TLK1-MK5 Axis Regulates Motility, Invasion, and Metastasis of Prostate Cancer Cells. Cancers 9 36497211
2021 Interaction of TLK1 and AKTIP as a Potential Regulator of AKT Activation in Castration-Resistant Prostate Cancer Progression. Pathophysiology : the official journal of the International Society for Pathophysiology 9 35366279
2005 Identification of the human DEAD-box protein p68 as a substrate of Tlk1. Biochemical and biophysical research communications 7 15950181
2023 The interaction between ASF1B and TLK1 promotes the malignant progression of low-grade glioma. Annals of medicine 4 36947060
2023 Exploiting TLK1 and Cisplatin Synergy for Synthetic Lethality in Androgen-Insensitive Prostate Cancer. Biomedicines 4 38001987
2024 De novo TLK1 and MDM1 mutations in a patient with a neurodevelopmental disorder and immunodeficiency. iScience 3 38868186
2024 A novel approach to investigate the combinatorial effects of TLK1 (Tousled-Like Kinase1) inhibitors with Temozolomide for glioblastoma therapy. Bioorganic chemistry 3 39029318
2024 TLK1>Nek1 Axis Promotes Nuclear Retention and Activation of YAP with Implications for Castration-Resistant Prostate Cancer. Cancers 3 39199688
2010 Caenorhabditis elegans TLK-1 controls cytokinesis by localizing AIR-2/Aurora B to midzone microtubules. Biochemical and biophysical research communications 3 20705056
2025 Characterization of new non-ATP dependent inhibitors of TLK1 as potential molecules for treating prostate cancer. Bioorganic chemistry 2 40058222
2023 Identification of a de novo mutation in TLK1 associated with a neurodevelopmental disorder and immunodeficiency. medRxiv : the preprint server for health sciences 2 37662408
2022 Circ_TLK1 knockdown alleviates oxygen-glucose deprivation/reoxygenation-induced PC12 cell injury by regulating microRNA-136-5p/follistatin like-1 axis. The European journal of neuroscience 2 35766911
2025 TLK1 as a therapeutic target in TMZ resistant glioblastoma using small molecule inhibitor. Scientific reports 1 40287404
2024 Autophosphorylation of the Tousled-like kinases TLK1 and TLK2 regulates recruitment to damaged chromatin via PCNA interaction. bioRxiv : the preprint server for biology 1 38712247
2024 TLK1 Inhibition Enhances the Anticancer Effect of Deep UV Irradiation Through CHK1 Activation. Anticancer research 1 38925844
2025 Autophosphorylation of the Tousled-like kinases TLK1 and TLK2 regulates recruitment to damaged chromatin via PCNA interaction. Nucleic acids research 0 39727191
2025 Targeting the TLK1-MK5 Axis Suppresses Prostate Cancer Metastasis. Cancers 0 40227796
2025 Mechanistic insights into Circ-MBOAT2-mediated regulation of TLK1 through miR-664b-3p in non-small cell lung cancer. Hereditas 0 40369698