Abstract
Dinoflagellates are marine unicellular eukaryotes that exhibit unique features including a very low level of basic proteins bound to the chromatin and the complete absence of histones and nucleosomal structure. A cDNA encoding a protein with a strong homology to the TATA box-binding proteins (TBP) has been isolated from an expressed sequence tag library of the dinoflagellate Crypthecodinium cohnii. The typical TBP repeat signature and the amino acid motives involved in TFIIA and TFIIB interactions were conserved in this new TBP-like protein. However, the four phenylalanines known to interact with the TATA box were substituted with hydrophilic residues (His(77), Arg(94), Tyr(171), Thr(188)) as has been described for TBP-like factors (TLF)/TBP-related proteins (TRP). A phylogenetic analysis showed that cTBP is intermediate between TBP and TLF/TRP protein families, and the structural similarity of cTBP with TLF was confirmed by low affinity binding to a consensus' TATA box in an equivalent manner to that usually observed for TLFs. Six 5'-upstream gene regions of dinoflagellate genes have been analyzed and neither a TATA box nor a consensus-promoting element could be found within these different sequences. Our results showed that cTBP could bind stronger to a TTTT box sequence than to the canonical TATA box, especially at high salt concentration. Same binding results were obtained with a mutated cTBP (mcTBP), in which the four phenylalanines were restored. To our knowledge, this is the first description of a TBP-like protein in a unicellular organism, which also appears as the major form of TBP present in C. cohnii.
Highlights
In higher eukaryotes, the regulation of transcription is intimately connected to the chromatin structure, and the accessibility of the transcription factors to their recognition elements is facilitated by the chromatin-remodeling processes involving a subset of modifying machines whose properties can alter the nucleosomal structure [1,2,3,4,5,6,7,8,9,10]
Presence of a Novel TATA box-binding Protein in the Dinoflagellate, C. cohnii—A 5Ј-oriented C. cohnii EST library was analyzed and an EST related to the TATA box-binding protein (TBP) family was identified using the Blast WWW-based program
In this work we describe for the first time in a unicellular eukaryotic organism a new class of transcription initiation factors that show intermediate structural features between the TBP and TBPlike factors (TLF)/TBP-related proteins (TRP) family of proteins
Summary
The regulation of transcription is intimately connected to the chromatin structure, and the accessibility of the transcription factors to their recognition elements is facilitated by the chromatin-remodeling processes involving a subset of modifying machines whose properties can alter the nucleosomal structure [1,2,3,4,5,6,7,8,9,10]. In mRNA synthesis, the transcription initiation step begins with the recognition of the promoter by the TFIID complex containing the TATA box-binding protein (TBP) and several TBP-associated factors [11,12,13,14,15]. In trypanosomatida (Kinetoplastidae) and trichomonadida (Parabasalia), neither the TATA box nor analogous sequences were detected among the few characterized genes Both showed an initiator element specific to each phylum (29 –31). The upstream gene organization is only known in the dinoflagellate species Gonyaulax polyedra for two genes: the peridinin chlorophyll-a-binding protein (PCP) and the luciferase genes [38, 39] These two genes exhibited a tandem repeat spaced by an intergenic region of about 1000 bp that contains a common 13-bp sequence, but no. We compared the binding of the cTBP and of a mutated form (mcTBP) to a TTTT box and to a canonical TATA box in various salt concentrations
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
