CTD small phosphatase 1(CTDSP1) Homo sapiens This gene encodes a member of the small C-terminal domain phosphatase (SCP) family of nuclear phosphatases. These proteins play a role in transcriptional regulation through specific dephosphorylation of phosphoserine 5 within tandem heptapeptide repeats of the C-terminal domain of RNA polymerase II. The encoded protein plays a role in neuronal gene silencing in non-neuronal cells, and may also inhibit osteoblast differentiation. Alternatively spliced transcript variants encoding multiple isoforms have been observed for this gene. [provided by RefSeq, Oct 2011]