| Modification Notes |
The family of small CTD phosphatases preferentially catalyze the dephosphorylation of Ser5 within a concensus repeat. As a member of this family, CTDSPL (CTD small phosphatase-like protein), also known as nuclear LIM interactor-interacting factor 1, RBSP3 or protein YA22, is a 276 amino acid nuclear protein that is ubiquitously expressed. There are two isoforms of CTDSPL that exist as a result of alternative splicing events. Since both of these isoforms reduce the level of phosphorylated Rb protein when transfected into mammary carcinoma cells, CTDSPL functions primarily as a phosphatase. The gene encoding CTDSPL is deleted in 15% of major epithelial cancers, suggesting that CTDSPL plays a role in tumor suppression. Due to evidence showing that inactive small CTD phosphatases interfere with the Repressor Element 1-silencing transcription factor/Neuron-Restrictive silencer factor (REST/NRSF) complex, therefore promoting neuronal differentiation, it is suspected that CTDSPL may function as a transcription regulator that acts to silence neuronal genes. |