title: A common structural scaffold in CTD phosphatases that supports distinct catalytic mechanisms.
abstract: The phosphorylation and dephosphorylation of the carboxyl-terminal domain (CTD) of the largest RNA polymerase II (RNAPII) subunit is a critical regulatory checkpoint for transcription and mRNA processing. This CTD is unique to eukaryotic organisms and it contains multiple tandem-repeats with the consensus sequence Tyr(1) -Ser(2) -Pro(3) -Thr(4) -Ser(5) -Pro(6) -Ser(7) . Traditionally, CTD phosphatases that use metal-ion-independent (cysteine-based) and metal-ion-assisted (aspartate-based) catalytic mechanisms have been considered to belong to two independent groups. However, using structural comparisons we have identified a common structural scaffold in these two groups of CTD phosphatases. This common scaffold accommodates different catalytic processes with the same substrate specificity, in this case phospho-serine/threonine residues flanked by prolines. Furthermore, this scaffold provides a structural connection between two groups of protein tyrosine phosphatases (PTPs): Cys-based (classes I, II, and III) and Asp-based (class IV) PTPs. Redundancy in catalytic mechanisms is not infrequent and may arise in specific biological settings. To better understand the activity of the CTD phosphatases, we combined our structural analyses with data on CTD phosphatase expression in different human and mouse tissues. The results suggest that aspartate- and cysteine-based CTD-dephosphorylation acts in concert during cellular stress, when high levels of reactive oxygen species can inhibit the nucleophilic function of the catalytic cysteine, as occurs in mental and neurodegenerative disorders like schizophrenia, Alzheimer's and Parkinson's diseases. Moreover, these findings have significant implications for the study of the RNAPII-CTD dephosphorylation in eukaryotes.
authors.affiliation: Structural Biology and BioComputing Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain.
authors.forename: Tirso
authors.initials: T
authors.lastname: Pons
authors.forename: Ida
authors.initials: I
authors.lastname: Paramonov
authors.forename: César
authors.initials: C
authors.lastname: Boullosa
authors.forename: Kristina
authors.initials: K
authors.lastname: Ibáñez
authors.forename: Ana M
authors.initials: AM
authors.lastname: Rojas
authors.forename: Alfonso
authors.initials: A
authors.lastname: Valencia
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D019295:Computational Biology; D030562:Databases, Protein; D019143:Evolution, Molecular; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D019696:Peptidylprolyl Isomerase / Q000737:chemistry / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D012319:RNA Polymerase II / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000201:enzymology; D013045:Species Specificity
chemical_list: D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D012319:RNA Polymerase II; D010749:Phosphoprotein Phosphatases; C116022:carboxy-terminal domain phosphatase; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase; C000606850:Pin1 protein, mouse
keywords: Alzheimer's disease; HAD superfamily; Parkinson's disease; RNA polymerase II carboxyl-terminal domain; catalytic mechanism; mental disorders; neurodegeneration; oxidative stress; prolyl cis/trans isomerization; protein phosphatases; schizophrenia; structure comparison