Isolation of cDNA, Chromosome Mapping, and Expression of the Human TBP-Like Protein

TBP is an essential factor for eukaryotic transcription. In this study, we identified a human cDNA encoding 21-kDa TBP-like protein (TLP). The TLP ORF, carrying 186 amino acids, covered the entire 180 amino acids of the C-terminal conserved domain of human TBP with 39% identity and 76% similarity. FISH determined that humantlpgene was located at chromosome 6 region q22.1-22.3. Northern blot analysis demonstrated that TLP mRNAs were expressed in various human tissues ubiquitously. We found that the TLP proteins exist in multiple mammalian cells and chicken cells. Although theDrosophilaTBP-related factor (TRF) is a neurogenesis-related transcription factor, expression of TLP was nearly constant throughout the neural differentiation of P19 cells. Unlike TRF, TLP did not bind to the TATA-box nor direct transcription initiationin vitro.Similarity between TRF and TLP was considerably lower (35 in alignment score) than that betweenDrosophilaTBP and human TBP (88 in alignment score). Multiple amino acids critical for the TBP function were deleted or substituted in TLP. We suggest that TLP is not abona fidevertebrate counterpart nor a direct descendant of TRF.