CTD small phosphatase-like protein (CTDSPL)

Recruited by REST to neuronal genes which contain RE-1 elements, resulting in neuronal gene silencing in non-neuronal cells (By similarity). Preferentially catalyzes the dephosphorylation of 'Ser-5' within the tandem 7 residue repeats in the C-terminal domain (CTD) of the largest RNA polymerase II subunit POLR2A.

Negatively regulates RNA polymerase II transcription, possibly by controlling the transition from initiation/capping into processive transcript elongation. .