Transcriptional activation by Sp1 and the adenovirus E1A transactivator protein

Abstract: Transcription is a key step in the regulation of gene expression. Activation of transcriptionrequires that the RNA polymerase receive both, regulatory signals from transcription factors,and initiate transcription at the correct location in the genome, at the promoter. A key issuedescribed in this thesis is the understanding of how transcription factors function to achievethe specificity required to regulate the complex pattern of gene expression. In particular,transcriptional regulation by the human Sp1 factor and the adenovirus encoded E1A proteinhave been studied.Sp1 is a ubiquitously expressed human transcription factor which regulatestranscription of several genes by synergistically interacting with a variety of transcriptionfactors, coactivators and TAFs. This thesis addresses whether Sp1 requires different regions,to mediate activation from two different RNA polymerase II promoters. Genetic studiesrevealed that overlapping but not identical parts of Sp1 were required for stimulation of aTATA box containing promoter and a U2 snRNA promoter. Moreover, this work describes the nature of the cooperativity between the transcription factors Sp1 and Oct-l. These factorswere found to cooperatively bind the U2 enhancer, as well as psychically interact, both in astandard in vitro binding approach, and in the yeast two hybrid system in vivo. The part ofSpl that bound to Oct-1 was found be located in a region necessary for transcriptionalstimulation of U2 transcription. Since there was a correlation between the in vitro interaction and the in vivo transcriptional activation, these results suggest that the physical interaction between these factors is of functional importance.Adenoviruses are small DNA viruses that use the mammalian transcriptionalmachinery to activate transcription of their own genes. This thesis describes the structuralfeatures of a novel region, termed auxiliary region 1 (AR1), located in the adenovirus encodedE1A protein. Genetic dissection of the AR1 region revealed, that E1A mediatedtranscriptional activation required the AR1 element in addition to the classicaltransactivation domain (CR3) for efficient activation of all early viral adenovirus promoters.Since the AR1 region is an essential element for viral transcription and located next to theCR3 region, this thesis suggest that the CR3 activation domain should be extended to alsoinclude AR1.