Regulatory interactions of the transcription fractor Sp1

Sp1 is a member of a family of closely related transcription factors which are indispensable for the activity of many promoters. Recently it turned out that Sp1 itself is tightly regulated. Interactions with cellular and viral proteins as well as posttranslational modifications like phosphorylation and glycosylation seem to influence Sp1 activity. We have investigated the interaction of Sp1 with histone deacetylase 1(HDAC 1). Together with acetyltransferases, histone deacetylases regulate the acetylation status of the DNA and thus the chromatin structure. HDAC 1 catalyzes the deacetylation of histones which results in chromatin condensation and shut down of transcription. But modification of histones is not the only way how acetyltransferases and deacetylases affect transcription. A growing number of transcription factors are also substrates for acetylation/deacetylation by the same proteins. One of these transcription factors seems to be Sp1. We could show that the interaction with HDAC 1 changes Sp1 to a negative regulator of promoter activity. That means that HDAC1 exerts at least part of its influence via the interaction with Sp1 and other members of the family. Aim of this project is to further investigate the role of Sp1 in the regulatory mechanisms which are controlled by acetylation/deacetylation. We will create mutants of Sp1 which cannot be acetylated any more and other mutants which are unable to bind HDAC 1. These mutants will be expressed and functionally tested by reporter gene assays in insect and mammalian cells. To scrutinize the relationship between the two proteins and the function of the acetylation of Sp1, we will use murine Sp1 -/- embryonic stem cells to establish cell lines expressing either wild type or specifically mutated forms of Sp1. The effects of the mutations on the activity of selected Sp1 dependent promoters as well as HDAC 1 influenced promoters will be examined.

Sp1 is a member of a family of closely related transcription factors which are indispensable for the activity of many promoters. Recently it turned out that Sp1 itself is tightly regulated. Interactions with cellular and viral proteins as well as posttranslational modifications like phosphorylation and glycosylation seem to influence Sp1 activity. We have investigated the interaction of Sp1 with histone deacetylase 1(HDAC 1). Together with acetyltransferases, histone deacetylases regulate the acetylation status of the DNA and thus the chromatin structure. HDAC 1 catalyzes the deacetylation of histones which results in chromatin condensation and shut down of transcription. But modification of histones is not the only way how acetyltransferases and deacetylases affect transcription. A growing number of transcription factors are also substrates for acetylation/deacetylation by the same proteins. One of these transcription factors seems to be Sp1. We could show that the interaction with HDAC 1 changes Sp1 to a negative regulator of promoter activity. That means that HDAC1 exerts at least part of its influence via the interaction with Sp1 and other members of the family. Aim of this project is to further investigate the role of Sp1 in the regulatory mechanisms which are controlled by acetylation/deacetylation. We will create mutants of Sp1 which cannot be acetylated any more and other mutants which are unable to bind HDAC 1. These mutants will be expressed and functionally tested by reporter gene assays in insect and mammalian cells. To scrutinize the relationship between the two proteins and the function of the acetylation of Sp1, we will use murine Sp1 -/- embryonic stem cells to establish cell lines expressing either wild type or specifically mutated forms of Sp1. The effects of the mutations on the activity of selected Sp1 dependent promoters as well as HDAC 1 influenced promoters will be examined.