Identification of a mouse TBP-like protein (TLP) distantly related to the Drosophila TBP-related factor

TATA-binding protein (TBP) is an essential factor for eukaryotic transcript ion. In this study, we demonstrated a mouse cDNA encoding a 21 kDa TBP-like protein (TLP). The TLP ORF, carrying 186 amino acids, covered the entire 1 80 amino acids of the C-terminal conserved domain of mouse TBP with 39% ide ntity and 76% similarity. Northern blot analysis demonstrated that TLP mRNA s were expressed in various mammalian tissues ubiquitously and that their d istribution pattern was analogous to that of TBP. By using anti-TLP antibod y, we demonstrated the existence of TLP proteins in various mammalian cells and tissues. The Drasophila TBP-related factor (TRF) is a neurogenesis-rel ated transcription factor that binds to the TATA-box and activates transcri ption. TLP did not bind to the TATA-box nor direct transcription initiation . Multiple amino acids critical for TBP function were deleted or substitute d in TLP, while amino acids in Drosophila TRF much resembled those in TBP. Similarity between Drosophila TRF and mouse TLP was considerably lower (ali gnment score 35) than that between Drosophila TBP and mouse TBP (alignment score 88). Identity of nucleotide sequences between mouse and putative huma n TLPs (94%) was higher than that between TBPs (91%) in these two animals. Expression of TLP was nearly constant throughout the P19 differentiation pr ocess. Accordingly we suggest that, even if higher eukaryotes generally con tain multiple tbp-related genes, TLP is not a bona fide mammalian counterpa rt of Drosophila TRF.