In vivo evidence that transcription and splicing are coordinated by a recruiting mechanism.

We describe the nuclear organization of pre-mRNA processing components in HeLa cells upon adenovirus 2 infection and their relationship to the localization of viral RNA sequences. We observe a redistribution of cellular splicing factors as well as RNA polymerase II and heterogeneous nuclear ribonucleoprotein particle proteins to sites of viral RNA transcription. Similar results were obtained in cells transiently transfected with a plasmid containing a portion of the beta-tropomyosin gene. Our findings demonstrate a very close association between RNA transcripts and transcription and pre-mRNA splicing factors, suggesting that these processes are both temporally and spatially linked in the cell nucleus. Furthermore, these data suggest a recruiting mechanism that regulates the localization of transcription and splicing factors in response to the initiation of active transcription.