TRANSCRIPTIONAL ACTIVATION MODULATED BY HOMOPOLYMERIC GLUTAMINE AND PROLINE STRETCHES

Many transcription factors contain proline- or glutamine-rich activati on domains. Here it is shown that simple homopolymeric stretches of th ese amino acids can activate transcription when fused to the DNA bindi ng domain of GAL4 factor. In vitro, activity increased with polymer le ngth, whereas in cell transfection assays maximal activity was achieve d by 10 to 30 glutamines or about 10 prolines. Similar results were ob tained when glutamine stretches were placed within a [GAL4]-VP16 chime ric protein. Because these stretches are encoded by rapidly evolving t riplet repeats (microsatellites), they may be the main cause for modul ation of transcription factor activity and thus result ir subtle or ov ert genomic effects.