Gene Expression covers the pathways by which genomic DNA is transcribed to yield RNA, the regulation of these transcription processes, and the pathways by which newly-made RNA Transcripts are processed. Most annotation is centered on the generation of messenger RNAs (mRNAs) by regulated RNA polymerase II (Pol II) transcription, although the activities of Pol I and Pol III are also covered briefly, as are some aspects of microRNA generation and function.
Aspects of mRNA synthesis annotated here include the assembly of transcription factor complexes and their role in targeting specific genes for transcription, Pol II mediated transcription (RNA synthesis) itself, and the co-translational and post-translational processing of this RNA, via capping, splicing, and 3'-cleavage and polyadenylation to yield mature mRNA molecules that are exported from the nucleus. mRNA editing and nonsense-mediated decay are also annotated. Processes leading to mRNA breakdown are described: deadenylation-dependent mRNA decay, microRNA-mediated RNA cleavage, and regulation of mRNA stability by proteins that bind AU-rich elements.
Other pathways included here are tRNA aminoacylation and snRNP assembly.