Function of the Genetic Material: Promoter Elements, RNA Polymerase, and Activator Proteins in Lower Eukaryotes

Abstract

Over the past several years an overwhelming number of observations have pointed to a surprisingly high degree of similarity in the molecular mechanisms of gene expression in eukaryotic cells, ranging from humans to yeasts (Guarente 1987, 1988). The view prevailing since the early observations on bacteria that gene expression is preponderandy regulated at the level of transcription has been strongly supported by innumerable contributions from all fields of eukaryotic genetics and molecular biology. The conservation of mechanisms in gene transcription of eukaryotic cells range from the subunit structure of RNA polymerase II and its catalytic properties, the posttranscriptional modifications of the primary transcripts, to the functional arrangements of elements in front of eukaryotic genes. Such elements, like UAS, TATA and silencer sequences are found in front of all eukaryotic protein-coding genes and are now regarded as crucial cis-acting determinants in eukaryotic gene expression, although the structure and arrangements which specify the function of promoters may vary considerably. In general, genes of higher eukaryotes display a more complex pattern in their promoter elements. For instance, activating elements in higher eukaryotic cells can lie also within structural genes or downstream of the transcript initiation site. Such downstream enhancers have not so far been detected in lower eukaryotes such as yeasts.