Analysis of the chicken TBP-like protein (tlp) gene: evidence for a striking conservation of vertebrate TLPs and for a close relationship between vertebrate tbp and tlp genes

TLP (TBP-like protein), which is a new protein discovered by us, has a stru cture similar to that of the C-terminal conserved domain (CCD) of TBP, alth ough its function has not yet been elucidated. We isolated cDNA and genomic DNA that encode chicken TLP (cTLP) and determined their structures, The pr edicted amino acid sequence of cTLP was 98 and 91% identical to that of its mammalian and Xenopus counterparts, respectively, and its translation prod uct was ubiquitously observed in chicken tissues, FISH detection showed tha t chicken tip and tbp genes were mapped at 3q2.6-2.8 and 3q2.4-2.6 of the s ame chromosome, respectively, Genome analysis revealed that the chicken tip gene was spliced with five introns, Interestingly, the vertebrate tbp gene s were also found to be split by five introns when we focused on the CCDs, and their splicing points were similar to those of tip, On the contrary, an other TBP-resembling gene of Drosophila, trf1, is split by only one intron, as is the Drosophila's tbp gene. These results support our earlier assumpt ion that vertebrate TLPs did not directly descend from Drosophila TRF1, On the basis of these results together with phylogenetical examination, we spe culate that tip diverged from an ancestral tbp gene through a process of ge ne duplication and point mutations.