|The spliceosome – the multimegadalton ribonucleoprotein complex, is one of the most elaborate macromolecular machines of the cell. Five small nuclear ribonucleoprotein particles (snRNPs) assemble in discrete complexes along a dynamic, energy-fueled pathway. Substantial structural and functional rearrangements along this route promote the catalytically competent spliceosomes that perform the two esterification reactions that excise intervening introns and ligate the exons of pre-mRNAs transcribed by RNA polymerase II. Splicing is largely co-transcriptional, and most genes in higher eukaryotes are subject to alternative splicing (AS). Alternative exons can be included or skipped, alternative 5’ and 3’ splice sites can be used and certain introns can be retained. AS vastly expands the repertoire of proteins and the range of their functional versatility. Chromatin dynamics and structure impact on transcription, splicing and alternative splicing. Splicing, in turn, affects transcriptional rates and the modulation of chromatin configuration. The pathways of transcription, splicing and chromatin modification and remodeling are entwined in a continuous, bidirectional partnership. Click here to explore the intricate spliceosomal pathway.