The overall aim of this thesis is to generate more knowledge on the mechanisms of eukaryotic transcription regulation with the focus on: 1) The effects of transcription elongation speed on regulation of gene expression and 2) the mechanisms of gene repression by transcriptional interference in plants. This thesis consists of four chapters: Chapter I is a manuscript for a review article, mainly reviewing the current knowledge of how histone PTMs are associated with and modulate the RNAPII transcription cycle, thus regulating plant development and response to environmental changes (Figure 1). Figure 1 Graphical abstract for Chapter I: A Genomic Positioning System for RNAPII transcription. Chapter II documents the major work of this thesis in a format of a manuscript. In brief, we generated Arabidopsis plant lines with altered RNAPII transcription kinetics through targeted mutagenesis of RNAPII subunit NRPB2. We demonstrated that accelerated RNAPII transcription reduces RNAPII genomic pausing and results in increased transcriptional read-through. Furthermore, we found that fast RNAPII exhibits higher accumulation profiles in gene bodies due to the reduced RNAPII pausing, which is associated with enhanced intron splicing. Mutant Arabidopsis with altered transcription kinetics exhibits global transcription variations and extreme phenotypes (Figure 2). Figure 2 Graphical abstract for Chapter II: Organismal benefits of controlling transcription speed at gene boundaries.