Jones, Robert Hugh; (1991) A study into the conserved nature of yeast and mammalian transcription factors. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The study of transcriptional regulation in mammalian cells has led to the identification of a large number of DNA binding transcription factors. Two such activities have been called ATF and AP1. The DNA sequence to which ATF binds to has been shown to mediate transcriptional activation by E1A and cAMP. On the other hand the AP1 binding site has been shown to mediate transcriptional activation by phorbol esters such as TPA. The consensus sequences of these two functional elements differ by only a single nucleotide but this difference is critical in determining specific transcription factor interaction. Previous studies have also defined sequence specific DNA binding proteins which can mediate transcriptional activation in S.cerevisiae. In this thesis I show that there are transcription factors in two yeast systems, that of S.cerevisiae and S.pombe, which have identical DNA binding specificities to the mammalian ATF and AP1 proteins. I have designated these proteins yATF and yAP1. In addition I show that viral promoters which contain binding sites for these transcription factors are expressed in S.pombe utililising transcriptional start sites also used in mammalian cells. By placing ATF and AP1 binding sites upstream of basal promoters I have demonstrated that S.pombe yAP1 and S.cerevisae yATF are most likely transcriptional activators. I have also shown that both the afore mentioned proteins are sensitive to phosphatase treatment indicating they are themselves phosphoproteins, a property which they would share with their mammalian counterparts. I have purified S.cerevisiae yAP1 and identified it as a major species of 85kd. In addition I have obtained a clone for a fission yeast protein which preferentially recognises an ATF site to an AP1 site by using a λgt11 expression library binding site screen. This work has provided the first demonstration of a fission yeast transcription factor. In addition it has shown a remarkable conservation in the DNA binding specificities of yeast and mammalian transcription factors. Together with the parallel developments which have taken place in this field this indicates that certain fundamental properties of the transcriptional machinery have been conserved throughout eukaryotes.

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