Tlk, a novel evolutionarily conserved murine serine threonine kinase, encodes multiple testis transcripts

Shalom, Sarah; Don, Jeremy

doi:10.1002/(sici)1098-2795(199904)52:4<392::aid-mrd8>3.0.co;2-y

Cited by 30 publications

(16 citation statements)

References 47 publications

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“…This suggests that Tlk genes may undergo differential splicing. In direct support of this view, a recent report describes differentially spliced Tlk2 transcripts in mouse testis (Shalom and Don, 1999).…”

Section: Isolation Of Two Distinct Human Tlk Cdnasmentioning

confidence: 76%

Mammalian homologues of the plant Tousled gene code for cell-cycle-regulated kinases with maximal activities linked to ongoing DNA replication

et al. 1999

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The Tousled (TSL) gene of the plant Arabidopsis thaliana encodes a serine/threonine kinase that is essential for proper flower development. Here we report the cloning and characterization of two human putative homologues of the Arabidopsis TSL gene, termed TLK1 and TLK2 (Tousled-like kinase). At the protein level, the two human Tlks share 84% sequence similarity with each other and almost 50% with Arabidopsis Tsl. Furthermore, nuclear localization signals and predicted coiled-coil regions are conserved in the N-terminal domains of all three kinases. The mammalian Tlks share several functional properties with plant Tsl, including a broad expression, a propensity to dimerize and autophosphorylate, and a preference for similar substrates. Most interestingly, human Tlks are cellcycle-regulated enzymes, displaying maximal activities during S phase. Whereas protein levels are virtually constant throughout the cell cycle, both Tlks appear to be regulated by cell-cycle-dependent phosphorylation. Drug-induced inhibition of DNA replication causes a rapid loss of Tlk activity, indicating that Tlk function is tightly linked to ongoing DNA replication. These findings provide the first biochemical clues as to the possible molecular functions of Tlks, a highly conserved family of kinases implicated in the development of multicellular organisms.

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Section: Isolation Of Two Distinct Human Tlk Cdnasmentioning

confidence: 76%

Mammalian homologues of the plant Tousled gene code for cell-cycle-regulated kinases with maximal activities linked to ongoing DNA replication

et al. 1999

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“…This was proposed to be linked to a replicative defect during organogenesis, but which may also result from failure to protect the genome from UV damage [2,3], resulting in mitotic aberrations [4-6]. Two Tousled genes (TLK1 and TLK2) were identified in mammals [7,8], and were confirmed as encoding kinases. Few physiologic substrates of Tousled like kinases (TLKs) have been identified, namely Asf1 [9], histone H3 [10], Aurora B [5], and more recently Rad9 in mammalian cells [11] and two mitotic kinesins in Trypanosomes [12].…”

Section: Introductionmentioning

confidence: 99%

TLK1B promotes repair of DSBs via its interaction with Rad9 and Asf1

2009

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BackgroundThe Tousled-like kinases are involved in chromatin assembly, DNA repair, transcription, and chromosome segregation. Previous evidence indicated that TLK1B can promote repair of plasmids with cohesive ends in vitro, but it was inferred that the mechanism was indirect and via chromatin assembly, mediated by its interaction with the chromatin assembly factor Asf1. We recently identified Rad9 as a substrate of TLK1B, and we presented evidence that the TLK1B-Rad9 interaction plays some role in DSB repair. Hence the relative contribution of Asf1 and Rad9 to the protective effect of TLK1B in DSBs repair is not known. Using an adeno-HO-mediated cleavage system in MM3MG cells, we previously showed that overexpression of either TLK1B or a kinase-dead protein (KD) promoted repair and the assembly of Rad9 in proximity of the DSB at early time points post-infection. This established that it is a chaperone activity of TLK1B and not directly the kinase activity that promotes recruitment of 9-1-1 to the DSB. However, the phosphorylation of Rad9(S328) by TLK1B appeared important for mediating a cell cycle checkpoint, and thus, this phosphorylation of Rad9 may have other effects on 9-1-1 functionality.ResultsHere we present direct evidence that TLK1B can promote repair of linearized plasmids with incompatible ends that require processing prior to ligation. Immunodepletion of Rad9 indicated that Rad9 was important for processing the ends preceding ligation, suggesting that the interaction of TLK1B with Rad9 is a key mediator for this type of repair. Ligation of incompatible ends also required DNA-PK, as addition of wortmannin or immunodepletion of Ku70 abrogated ligation. Depletion of Ku70 prevented the ligation of the plasmid but did not affect stimulation of the fill-in of the ends by added TLK1B, which was attributed to Rad9. From experiments with the HO-cleavage system, we now show that Rad17, a subunit of the "clamp loader", associates normally with the DSB in KD-overexpressing cells. However, the subsequent release of Rad17 and Rad9 upon repair of the DSB was significantly slower in these cells compared to controls or cells expressing wt-TLK1B.ConclusionsTLKs play important roles in DNA repair, not only by modulation of chromatin assembly via Asf1, but also by a more direct function in processing the ends of a DSB via interaction with Rad9. Inhibition of Rad9 phosphorylation in KD-overexpressing cells may have consequences in signaling completion of the repair and cell cycle re-entry, and could explain a loss of viability from DSBs in these cells.

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“…TOUSLED-like kinases (TLKs) are highly conserved and are found in both plants and animals. Humans and mice both have two highly related TLK genes, TLK1 and TLK2 (Yamakawa et al, 1997;Shalom and Don, 1999;Sillje et al, 1999;Zhang et al, 1999;Li et al, 2001). Human TLK expression is constitutive throughout the cell cycle, while TLK protein kinase activity (both TLK1 and TLK2) oscillates during the cell cycle, with a peak of activity in S-phase (Sillje et al, 1999).…”

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confidence: 99%

TOUSLED Kinase Activity Oscillates during the Cell Cycle and Interacts with Chromatin Regulators

et al. 2004

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The TOUSLED (TSL)-like nuclear protein kinase family is highly conserved in plants and animals. tsl loss of function mutations cause pleiotropic defects in both leaf and flower development, and growth and initiation of floral organ primordia is abnormal, suggesting that basic cellular processes are affected. TSL is more highly expressed in exponentially growing Arabidopsis culture cells than in stationary, nondividing cells. While its expression remains constant throughout the cell cycle in dividing cells, TSL kinase activity is higher in enriched late G2/M-phase and G1-phase populations of Arabidopsis suspension culture cells compared to those in S-phase. tsl mutants also display an aberrant pattern and increased expression levels of the mitotic cyclin gene CycB1;1, suggesting that TSL represses CycB1;1 expression at certain times during development or that cells are delayed in mitosis. TSL interacts with and phosphorylates one of two Arabidopsis homologs of the nucleosome assembly/ silencing protein Asf1 and histone H3, as in humans, and a novel plant SANT/myb-domain protein, TKI1, suggesting that TSL plays a role in chromatin metabolism.TOUSLED (TSL) is a widely expressed gene in Arabidopsis required for proper development (Roe et al., 1993(Roe et al., , 1997b. TSL is a nuclear Ser/Thr protein kinase composed of a C-terminal catalytic domain and an N-terminal regulatory domain (Roe et al., 1997a). TOUSLED-like kinases (TLKs) are highly conserved and are found in both plants and animals. Humans and mice both have two highly related TLK genes, TLK1 and TLK2 (Yamakawa et al., 1997;Shalom and Don, 1999;Sillje et al., 1999;Zhang et al., 1999;Li et al., 2001). Human TLK expression is constitutive throughout the cell cycle, while TLK protein kinase activity (both TLK1 and TLK2) oscillates during the cell cycle, with a peak of activity in S-phase (Sillje et al., 1999). Inhibition of DNA polymerase a causes a decrease in TLK activity, suggesting that activation of TLKs is linked to DNA replication (Sillje et al., 1999). In addition, recent evidence indicates that TLKs are targets of DNA damage checkpoints (Groth et al., 2003). Mutations in TLK genes cause severe defects in both plants and animals; tsl loss-of-function mutations in Arabidopsis cause flower and leaf abnormalities (Roe et al., 1993), whereas mutations in or suppression of TLK homologs in Drosophila melanogaster and Caenorhabditis elegans cause an early arrest in the embryo (Carrera et al., 2003;Han et al., 2003; T. Ratliff, M. Herman, and J. Roe, unpublished data). Overexpression of TLK1 in mouse cells conferred enhanced resistance to ionizing radiation (Li et al., 2001). A dominant negative form caused missegregation of chromosomes, whereas siRNA-mediated suppression of TLK1 blocked cell division in mouse cells (SunavalaDossabhoy et al., 2003).The target(s) of TSL and the TLKs have remained elusive until recently. Sillje and Nigg (2001) identified the human homolog of Asf1 (also known as CIA) as a candidate TLK target. Asf1 is a silencing protein first ...

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Tlk, a novel evolutionarily conserved murine serine threonine kinase, encodes multiple testis transcripts

Cited by 30 publications

References 47 publications

Mammalian homologues of the plant Tousled gene code for cell-cycle-regulated kinases with maximal activities linked to ongoing DNA replication

Mammalian homologues of the plant Tousled gene code for cell-cycle-regulated kinases with maximal activities linked to ongoing DNA replication

TLK1B promotes repair of DSBs via its interaction with Rad9 and Asf1

TOUSLED Kinase Activity Oscillates during the Cell Cycle and Interacts with Chromatin Regulators

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