{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n CTDP1 encodes the RNA polymerase II C‐terminal domain (CTD) phosphatase FCP1, an enzyme essential for efficient transcription in eukaryotic cells. FCP1 dephosphorylates the serine residues (Ser2 and Ser5) within the heptapeptide repeats of the RNAPII CTD, a key step that promotes recycling of RNAPII and facilitates the transition from transcription initiation to elongation (see."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "6"}]}, {"type": "t", "text": " In this context, FCP1 functions as a pivotal hub in transcription regulation by interacting with general transcription factors such as TFIIF—the RAP74 subunit of which not only directly binds FCP1 but also stimulates its enzymatic activity—and TFIIB; its activity is further modulated by its own phosphorylation state and by regulatory proteins like HIV-1 Tat."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Beyond its classical role in transcription, CTDP1/FCP1 is also implicated in cell cycle regulation—for example, by coordinating dephosphorylation cascades that are critical for mitotic exit."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": " Importantly, loss-of-function mutations in CTDP1, such as a single-nucleotide substitution leading to aberrant splicing, cause congenital cataracts-facial dysmorphism-neuropathy (CCFDN) syndrome, thereby underscoring the critical role of CTDP1 in development (see."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": " Moreover, autoantibodies directed against CTDP1 have been identified as a specific marker in Behçet disease, which further highlights its clinical significance."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "10"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n In summary, CTDP1 is central to maintaining proper transcriptional dynamics by dephosphorylating the RNAPII CTD, thereby ensuring efficient polymerase recycling and accurate transcription elongation. This function is intricately regulated through its interactions with transcription factors and post-translational modifications, and its disruption is linked to developmental syndromes and immune-mediated disease. \n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Patrick S Lin, Marie-Francoise Dubois, Michael E Dahmus "}, {"type": "b", "children": [{"type": "t", "text": "TFIIF-associating carboxyl-terminal domain phosphatase dephosphorylates phosphoserines 2 and 5 of RNA polymerase II."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "J Biol Chem (2002)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1074/jbc.M208588200"}], "href": "https://doi.org/10.1074/jbc.M208588200"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "12351650"}], "href": "https://pubmed.ncbi.nlm.nih.gov/12351650"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Subhrangsu S Mandal, Helen Cho, Sungjoon Kim, et al. "}, {"type": "b", "children": [{"type": "t", "text": "FCP1, a phosphatase specific for the heptapeptide repeat of the largest subunit of RNA polymerase II, stimulates transcription elongation."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Mol Cell Biol (2002)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1128/MCB.22.21.7543-7552.2002"}], "href": "https://doi.org/10.1128/MCB.22.21.7543-7552.2002"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "12370301"}], "href": "https://pubmed.ncbi.nlm.nih.gov/12370301"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Bao D Nguyen, Karen L Abbott, Krzysztof Potempa, et al. 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