Identification of a phosphatase activity, toward the phosphopeptide pyroGlu-Asp-Asp-Ser(p)-Asp-Glu-Glu-Asn, in nuclear extract from HL-60 promyelocitic leukaemia cells.

Total protein extract from HL-60 cells was found to be able to dephosphorylate the RNA polymerase II octapeptide pyroGlu-Asp-Asp-Ser-Asp-Glu-Glu-Asn previously phosphorylated with protein kinase CKII (pCKII). Fractionation in cytoplasm, nuclear and chromatin extracts shows the phosphatase activity to be localized only in the nucleus, but not to be bound to the chromatin.