Emerging roles for RNA polymerase II CTD in Arabidopsis

• We examine regulation of transcription and RNA processing through CTD modifications.
• We highlight elements regulating post-translational modification of the CTD.
• Plants lack key regulatory components involved in promoter-proximal pausing.
• Plants lack key components of the Nrd1-dependent transcription termination pathway.
• RNAPII CTD phosphorylation is required for miRNA biogenesis.

Post-translational modifications of the carboxy-terminal domain of the largest subunit of RNA polymerase II (RNAPII CTD) provide recognition marks to coordinate recruitment of numerous nuclear factors controlling transcription, cotranscriptional RNA processing, chromatin remodeling, and RNA export. Compared with the progress in yeast and mammals, deciphering the regulatory roles of position-specific combinatorial CTD modifications, the so-called CTD code, is still at an early stage in plants. In this review, we discuss some of the recent advances in understanding of the molecular mechanisms controlling the deposition and recognition of RNAPII CTD marks in plants during the transcriptional cycle and highlight some intriguing differences between regulatory components characterized in yeast, mammals, and plants.