Fig. 1. (A) Schematic representation of the mouse Ciz1 protein, which is approximately 70% homologous to human Ciz1. Several of the amino acid sequence features detected by Prosite (http://us.expasy.org/prosite/) are indicated in the key. Analysis of expressed sequence tags that map to the Ciz1 Unigene Cluster Hs.212395 (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=unigene) indicates that at least four exons are alternatively spliced in transcripts from a wide range of tissues. Three of these (indicated in red) are absent from a Ciz1 variant cloned from a mouse embryo-derived cDNA library, designated ECiz1 (Coverley et al., 2005). From left to right these are part exons 2, 6 and 8. This analysis focuses on full-length Ciz1 (845 amino acids) and the ECiz1 variant (708 amino acids). Green ovals indicate the presence of a GFP tag attached to the N terminus of both variants. (B) Ectopic GFP-Ciz1 and GFP-ECiz1 form foci in the nucleus of NIH3T3 cells. Representative confocal images of GFP fluorescence taken 20 and 44 hours after transfection are shown. Bar, 10 µm.