Co-Phosphoregulatory Network Underlying Functional Coherence of TLK1 and TLK2 Kinase Paralogs

Tousled-like kinases 1 and 2 (TLK1 and TLK2) are paralogous serine/threonine kinases that share high sequence similarity yet exhibit functional divergence in cellular processes such as DNA replication, damage response, and chromatin organization. This study elucidates the paralog-specific co-phosphoregulatory networks underlying this divergence through a comprehensive analysis of 3825 human phosphoproteomic articles. Predominant phosphosites were identified as S134 and T38 for TLK1 and S73, S99, and S111 for TLK2, revealing context-dependent regulation across cancers and perturbations. Co-phosphoregulation analyses uncovered distinct networks: TLK1 associates with DNA damage signaling via proteins like ABRAXAS1, PML, and RAD9A, while TLK2 integrates with chromatin remodeling and replication through CHD4, DOT1L, NASP, and RNF20. Upstream kinases for TLK2, predominantly CDKs, link it to cell-cycle progression, whereas downstream substrates and binary interactors converge on genome stability pathways with paralog-specific nuances. These findings highlight the potential role of TLK1 on checkpoint activation and TLK2 on replication-coupled chromatin maintenance, providing insights into their roles in cancer amplification and therapeutic resistance, as well as neurodevelopmental disorders, where emerging evidence also support the involvement of TLK1 alongside TLK2.