Fig. 1.
Electron- and light-microscopic visualization of BR mRNPs. (A) Electron microscopy of BR particles in the nucleoplasm of C. tentans salivary-gland cells. Four BR particles are indicated by thin arrows. A minor portion of a BR is demarcated to the left by an dashed line. A segment of an active gene with growing RNP particles has been marked by a thick arrow. (B) A C. tentans salivary-gland cell nucleus imaged in an LSM 5 Live after microinjection of LgBR-Oligo-Cy5. The white arrows indicate single BR mRNPs. (C) Time course of the fluorescence in a living C. tentans salivary-gland cell nucleus after addition of DRB, an inhibitor of RNA polymerase-II-dependent transcription. The characteristic labeling of the BR2 by LgBR-Oligo-Cy5 is lost within 10 min. This observation indicates that the oligonucleotide probe labeled growing BR2 mRNPs and not the BR2 DNA.