Abstract

Speckles are subnuclear structures that are enriched in pre-messenger RNA splicing factors and are located in the interchromatin regions of the nucleoplasm of mammalian cells. At the fluorescence-microscope level they appear as irregular, punctate structures, which vary in size and shape, and when examined by electron microscopy they are seen as clusters of interchromatin granules. Speckles are dynamic structures, and both their protein and RNA–protein components can cycle continuously between speckles and other nuclear locations, including active transcription sites. Studies on the composition, structure and behaviour of speckles have provided a model for understanding the functional compartmentalization of the nucleus and the organization of the gene-expression machinery.

Author affiliations

1. Wellcome Trust Biocentre, Medical Sciences Institute/Wellcome Trust Biocentre Complex, University of Dundee, Dundee DD1 5EH, UK.
   Email: a.i.lamond@dundee.ac.uk
2. Cold Spring Harbor Laboratory, One Bungtown Road, Cold Spring Harbor, New York 11724, USA.
   Email: spector@cshl.edu