Fig. 1. Organization of the TUB, TULP3 and TULP1 proteins. Each box represents amino acids translated from each exon, and the percentage amino-acid sequence similarity with TUB is shown. Green boxes indicate the N-terminal regions with relatively low homology between family members. Red boxes indicate the C-terminal regions with high homology. The blue boxes represent the common acceptor site for alternative N-terminal exons observed in both human and mouse TUB. Yellow and pink boxes represent exons that are not conserved among family members. The nuclear localization signal is indicated. The N-terminal regions of TUB and TULP1 are able to activate transcription; the C-terminal region of TUB can bind to double-stranded DNA and to phosphatidylinositol-phosphates.