RNA-dependent DNA binding activity of the Pur factor, potentially involved in DNA replication and gene transcription

The PUR element is a polypurine polypyrimidine motif that can stimulate transcription, encountered in the 5' regions of various genes and in the vicinity of several DNA replication initiation zones. We demonstrate that the PUR complex formation between the purine-rich strand of PUR and nuclear extracts can be prevented by pretreatment of nuclear extracts with RNA-damaging agents such as UV light or RNase A. A biochemical affinity method reveals that small RNA molecules copurify with the Pur factor. Moreover, the PUR binding activity of RNA-depleted nuclear extracts can be restored by addition of phenol-extracted RNAs. This work adds a new member in the emerging class of ribonucleoprotein particles as regulatory factors of the genetic expression.