Differential requirements for Tousled-like kinases 1 and 2 in mammalian development

Abstract

The regulation of chromatin structure is critical for a wide range of essential cellular processes. The Tousled-like kinases, TLK1 and TLK2, regulate ASF1, a histone H3/H4 chaperone, and likely other substrates, and their activity has been implicated in transcription, DNA replication, DNA repair, RNA interference, cell cycle progression, viral latency, chromosome segregation and mitosis. However, little is known about the functions of TLK activity in vivo or the relative functions of the highly similar TLK1 and TLK2 in any cell type. To begin to address this, we have generated Tlk1- and Tlk2-deficient mice. We found that while TLK1 was dispensable for murine viability, TLK2 loss led to late embryonic lethality because of placental failure. TLK2 was required for normal trophoblast differentiation and the phosphorylation of ASF1 was reduced in placentas lacking TLK2. Conditional bypass of the placental phenotype allowed the generation of apparently healthy Tlk2-deficient mice, while only the depletion of both TLK1 and TLK2 led to extensive genomic instability, indicating that both activities contribute to genome maintenance. Our data identifies a specific role for TLK2 in placental function during mammalian development and suggests that TLK1 and TLK2 have largely redundant roles in genome maintenance.

De Novo and Inherited Loss-of-Function Variants in TLK2: Clinical and Genotype-Phenotype Evaluation of a Distinct Neurodevelopmental Disorder

“… 7 Tlk2 -null mice were embryonically lethal due to placental failure. 15 In this study, we found several predicted LOF variants in affected individuals. To investigate whether variants resulted in an aberrant transcript, we synthesized cDNA from RNA extracted from fibroblast or lymphoblastoid cell lines ( Supplemental Subjects and Methods , Table S7 ) from three individuals with different variants: (1) c.989C>A (p.Ser330 ∗ ), predicted to result in a truncated product leading to nonsense-mediated decay (NMD); (2) c.2092C>T (p.Arg698 ∗ ), with a premature stop codon in the last exon predicted to escape from NMD; and (3) c.1720+1G>T, a mutation predicted to affect splicing of exon 18.…”

High yield bacterial expression, purification and characterisation of bioactive Human Tousled-like Kinase 1B involved in cancer

“…Further evidence on TLK2 autophosphorylation comes from the thesis work of Helena Gonzalez Buron (University of Barcelona, Spain) who confirmed that the residue S 635, located in the TLK2 activation loop, is a crucial TLK2 autophosphorylation site and could be required for TLK2 activity. However, further cellular assays are necessary to validate its functional relevance 35 . Since the kinase domain is highly conserved between TLK1/1B and TLK2, we predict a corresponding residue in TLK1/1B may be involved in its activation and autophosphorylation.…”

Using Human iPSC-Derived Neurons to Uncover Activity-Dependent Non-Coding RNAs

“…It is interesting that two structural homologues have neurological or immunological roles, maybe as a result of both systems being highly adaptable and evolutionarily and developmentally interlinked [ 68 , 69 ]. TLK2 , another differentially expressed gene is required for placental development and, while coupling with TLK1 , supports genomic stability in mice by recovery of damaged DNA in preparation for mitosis [ 70 , 71 ]. When coupled with ASF1 , TLK2 restores chromatin structure after DNA damage and assists further progression through the cell cycle [ 71 ].…”