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J. Biol. Chem., Vol. 277, Issue 43, 40881-40886, October 25, 2002
From the 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 (His77, Arg94,
Tyr171, Thr188) 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.
Copyright © 2002 by The American Society for Biochemistry and Molecular Biology, Inc. This article has been cited by other articles:
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