Serine/threonine-protein kinase which is required for checkpoint-mediated cell cycle arrest and activation of DNA repair in response to the presence of DNA damage or unreplicated DNA (PubMed:15326393). May also negatively regulate cell cycle progression during unperturbed cell cycles (PubMed:15326393). Required for checkpoint mediated cell cycle arrest in response to DNA damage in germline cells (PubMed:15326393, PubMed:27956467). Delays cell-cycle reentry of the Z2 and Z3 primordial germ cells in response to transcription-induced DNA damage as they emerge from cell cycle arrest in L1 larvae (PubMed:26073019). Essential for embryogenesis (PubMed:15326393). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] The Ser-344 phosphorylated form colocalizes with P granules in a perinuclear manner in embryonic germline precursor cells and in Z2/Z3 primordial germ cells in L1 stage larvae. Expressed in the germline. Highly expressed in the embryo. RNAi-mediated knockdown leads to premature cell-cycle reentry of the Z2/Z3 primordial germ cells in L1 stage larvae (PubMed:26073019). RNAi-mediated knockdown and DNA damage induced by the ribonucleotide reductase inhibitor hydroxyurea in germ cells results in impaired DNA repair, but does allow for nuclear division (PubMed:27956467). In the proliferative zone of these germ cells, nuclei do not arrest following DNA damage, but prematurely divide and are smaller compared to wild-type (PubMed:27956467). Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family. NIM1 subfamily. Truncated N-terminus.