Fluorescent RNA cytochemistry: tracking gene transcripts in living cells

The advent of jellyfish green fluorescent protein and its spectral variants , together with promising new fluorescent proteins from other classes of th e Cnidarian phylum (coral and anemones), has greatly enhanced and promises to further boost the detection and localization of proteins in cell biology . It has been less widely appreciated that highly sensitive methods have al so recently been developed for detecting the movement and localization in l iving cells of the very molecules that precede proteins in the gene express ion pathway, i.e. RNAs, These approaches include the microinjection of fluo rescent RNAs into living cells, the in vivo hybridization of fluorescent ol igonucleotides to endogenous RNAs and the expression in cells of fluorescen t RNA-binding proteins, This new field of 'fluorescent RNA cytochemistry' i s summarized in this article, with emphasis on the biological insights it h as already provided. These new techniques are likely to soon collaborate wi th other emerging approaches to advance the investigation of RNA birth, RNA -protein assembly and ribonucleoprotein particle transport in systems such as oocytes, embryos, neurons and other somatic cells, and may even permit t he observation of viral replication and transcription pathways as they proc eed in living cells, ushering in a new era of nucleic acids research in viv o.