title: CDKF;1 and CDKD protein kinases regulate phosphorylation of serine residues in the C-terminal domain of Arabidopsis RNA polymerase II.
abstract: Phosphorylation of conserved Y₁S₂P₃T₄S₅P₆S₇ repeats in the C-terminal domain of largest subunit of RNA polymerase II (RNAPII CTD) plays a central role in the regulation of transcription and cotranscriptional RNA processing. Here, we show that Ser phosphorylation of Arabidopsis thaliana RNAPII CTD is governed by CYCLIN-DEPENDENT KINASE F;1 (CDKF;1), a unique plant-specific CTD S₇-kinase. CDKF;1 is required for in vivo activation of functionally redundant CYCLIN-DEPENDENT KINASE Ds (CDKDs), which are major CTD S₅-kinases that also phosphorylate in vitro the S₂ and S₇ CTD residues. Inactivation of CDKF;1 causes extreme dwarfism and sterility. Inhibition of CTD S₇-phosphorylation in germinating cdkf;1 seedlings is accompanied by 3'-polyadenylation defects of pre-microRNAs and transcripts encoding key regulators of small RNA biogenesis pathways. The cdkf;1 mutation also decreases the levels of both precursor and mature small RNAs without causing global downregulation of the protein-coding transcriptome and enhances the removal of introns that carry pre-microRNA stem-loops. A triple cdkd knockout mutant is not viable, but a combination of null and weak cdkd;3 alleles in a triple cdkd123* mutant permits semidwarf growth. Germinating cdkd123* seedlings show reduced CTD S₅-phosphorylation, accumulation of uncapped precursor microRNAs, and a parallel decrease in mature microRNA. During later development of cdkd123* seedlings, however, S₇-phosphorylation and unprocessed small RNA levels decline similarly as in the cdkf;1 mutant. Taken together, cotranscriptional processing and stability of a set of small RNAs and transcripts involved in their biogenesis are sensitive to changes in the phosphorylation of RNAPII CTD by CDKF;1 and CDKDs.
authors.affiliation: Department of Plant Developmental Biology, Max-Planck Institute for Plant Breeding Research, D-50829 Cologne, Germany.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Hajheidari
authors.forename: Sara
authors.initials: S
authors.lastname: Farrona
authors.forename: Bruno
authors.initials: B
authors.lastname: Huettel
authors.forename: Zsuzsa
authors.initials: Z
authors.lastname: Koncz
authors.forename: Csaba
authors.initials: C
authors.lastname: Koncz
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D053898:Biosynthetic Pathways / Q000235:genetics; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D015536:Down-Regulation / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009693:Nucleic Acid Hybridization; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012315:RNA Caps / Q000378:metabolism; D012319:RNA Polymerase II / Q000737:chemistry* / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics; D012326:RNA Splicing / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D022661:RNA, Untranslated / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D035683:MicroRNAs; D012315:RNA Caps; D012322:RNA Precursors; D012333:RNA, Messenger; D018749:RNA, Plant; D034741:RNA, Small Interfering; D022661:RNA, Untranslated; D010768:Phosphoserine; C112244:Cak1at protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D018844:Cyclin-Dependent Kinases; D012319:RNA Polymerase II