During the late stages of oogenesis, dephosphorylates 'Ser-5' of the heptad repeats YSPTSPS in the C-terminal domain of the largest RNA polymerase II subunit ama-1 (PubMed:17291483). Similarly, dephosphorylates 'Ser-5' of ama-1 in early embryonic cells prior to the activation of the zygotic transcription program at the 4-cell embryonic stage (PubMed:17291483). May dephosphorylate 'Ser-2' of the ama-1 heptad repeats YSPTSPS in embryonic somatic and germline cells (PubMed:23903194). H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate RNAi-mediated knockdown causes an arrest at the 100-cell embryonic stage (PubMed:17291483). In developing oocytes, results in an abnormal accumulation of 'Ser-5' phosphorylated ama-1 and a more diffused nuclear localization of phosphorylated ama-1 (PubMed:17291483). 'Ser-2' phosphorylated ama-1 is present in diakinetic oocyte but at low levels indicating that transcription is possibly blocked at the elongation stage (PubMed:17291483). Increased levels of 'Ser-2' phosphorylated ama-1 in embryonic and germline nuclei (PubMed:23903194). Simultaneous knockdown of components of the transcription pre-initiation complex including ama-1, rbp-2, cdk-7, rgr-1 or taf-4 abolishes phosphorylation of the ama-1 CTD domain repeats at 'Ser-5' in diakinetic oocytes (PubMed:17291483). A similar abnormal accumulation of 'Ser-5' phosphorylated ama-1 occurs in 1-cell and 2-cell embryos (PubMed:17291483).