THE NSSBF ELEMENT, A SEQUENCE OF THE DROSOPHILA-MELANOGASTER RETROTRANSPOSON-1731 POTENTIALLY IMPLICATED IN TRANSCRIPTIONAL REPRESSION AND REPLICATION

The nuclear single-stranded DNA binding factor (NssBF) has been charac terized as a nuclear protein that binds to a 26 nucleotides sequence i n the long terminal repeat (LTR) of the Drosophila melanogaster 1731 r etrotransposon. This sequence, called NssBF element, mas analysed by g el retardation experiments using wild-type and mutated oligonucleotide s. In vitro transcription experiments were performed and suggest that NssBF element binding protein(s) represses transcription through the 1 731 promoter. Furthermore, computer assisted sequence comparisons put forward a possible role of this element and/or its associated DNA bind ing proteins in replication.