Journal Article

CDKF;1 and CDKD Protein Kinases Regulate Phosphorylation of Serine Residues in the C-Terminal Domain of Arabidopsis RNA Polymerase II

Farrona, Sara, Hajheidari, Mohsen, Koncz, Zsuzsa, Koncz, Csaba, Huettel, Bruno

2012

Overview

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 premicroRNA 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.

• Publisher: American Society of Plant Biologists
• Subject: alleles / Arabidopsis / Arabidopsis - enzymology / Arabidopsis - genetics / Arabidopsis - growth & development / Arabidopsis Proteins / Arabidopsis Proteins - chemistry / Arabidopsis Proteins - genetics / Arabidopsis Proteins - metabolism / Arabidopsis thaliana / biosynthesis / Biosynthetic Pathways / Biosynthetic Pathways - genetics / chemistry / cyclin-dependent kinase / Cyclin-Dependent Kinases / Cyclin-Dependent Kinases - metabolism / DNA-directed RNA polymerase / Down-Regulation / Down-Regulation - genetics / enzymology / gene expression regulation / Gene Expression Regulation, Plant / Genes / Genes, Plant / Genes, Plant - genetics / Genetic mutation / genetics / growth & development / Inactivation / knockout mutants / messenger RNA / metabolism / MicroRNA / MicroRNAs / MicroRNAs - genetics / MicroRNAs - metabolism / mutation / Mutation - genetics / Nucleic Acid Hybridization / Phosphorylation / Phosphoserine / Phosphoserine - metabolism / Plant cells / Protein Serine-Threonine Kinases / Protein Structure, Tertiary / Protein-Serine-Threonine Kinases - metabolism / Proteins / RNA / RNA Caps / RNA Caps - metabolism / RNA Polymerase II / RNA Polymerase II - chemistry / RNA Polymerase II - metabolism / RNA Precursors / RNA Precursors - metabolism / RNA Processing, Post-Transcriptional / RNA Processing, Post-Transcriptional - genetics / RNA Splicing / RNA Splicing - genetics / RNA, Messenger / RNA, Messenger - genetics / RNA, Messenger - metabolism / RNA, Plant / RNA, Plant - biosynthesis / RNA, Plant - genetics / RNA, Small Interfering / RNA, Small Interfering - genetics / RNA, Small Interfering - metabolism / RNA, Untranslated / RNA, Untranslated - genetics / Seedlings / serine / transcription (genetics) / Transcription, Genetic / transcriptome / Yeasts