Transcriptional elongation by RNA polymerase II (RNAPII) is a dynamic and highly regulated step of the transcription cycle. Accordingly, multiple so-called transcript elongation factors (including modulators of RNAPII activity, histone chaperones, histone modifiers) were identified that control the synthesis of mRNAs. Proteomic studies demonstrated that several of these factors form with RNAPII a transcript elongation complex in Arabidopsis. In addition, a variety of pre-mRNA splicing and polyadenylation factor as well as mRNA export factors were found to associate with this complex and/or nascent transcripts. Therefore, the RNAPII elongation complex serves as a platform coordinating ongoing transcription with mRNA processing and export.