Extremely reduced evolutionary rate of TATA-box binding protein in higher vertebrates and its evolutionary implications

Abstract

Previously we showed that the evolutionary rates of the Pax proteins are markedly reduced in higher vertebrates, as compared with those in the ancestral lineage of vertebrates, and we suggested that the reduced Pax protein evolution might be explained by increased functional constraints due to gene recruitment for other purposes or repeated expression in different developmental stages. To clarify the problem of whether the evolutionary rate variation found in the Pax proteins is an evolutionary feature generally recognized in most transcription factors, we have cloned and sequenced cDNAs encoding the TATA-box binding protein (TBP), a general transcription factor of eukaryotes, from Oryzias latipes, a Japanese medaka, Lampetra reissneri, a lamprey, and Ephydatia fluviatilis, a freshwater sponge. An evolutionary rate analysis of TBP has revealed that the evolutionary rate of TBP is extremely low in higher vertebrates, but not in the ancestral lineage of vertebrates, as found in the Pax proteins. In contrast, no marked reduction of the evolutionary rate in higher vertebrates is observed in the aldolase C, a house keeping enzyme. It is therefore likely that the increased functional constraint on TBP is responsible for the extremely low evolutionary rate in higher vertebrates. The temporal pattern of the evolutionary rate variation during vertebrate evolution was discussed.