Dynamic organization of pre-mRNA splicing factors

Studies from several laboratories during the past few years have increased our understanding towards the dynamic organization of pre‐mRNA splicing factors in the mammalian cell nucleus. Many well characterized splicing factors have been localized in a speckled pattern in the cell nucleus. Upon the activation of RNA polymerase II transcription, splicing factors are recruited to the sites of transcription from sites of reassembly and/or storage. Nascent intron‐containing RNA transcripts are spliced at the sites of transcription. The speckled distribution of splicing factors in the nucleus is altered when either transcription or pre‐mRNA splicing activities are interrupted suggesting that the organization of the splicing machinery in the interphase nucleus is a direct reflection of the transcriptional activity of the cell. © 1996 Wiley‐Liss, Inc.