Identification of a protein that binds specifically to RNA from the first exon of c-myc.

A 55 kilodalton protein present in HeLa and MEL cells, which binds specifically to RNA derived from the first exon of the human c-myc gene, has been identified using a UV-induced crosslinking assay. This protein, called p55, is found in both cytoplasmic and nuclear fractions. The binding site on the RNA, defined using deletion analysis and synthetic oligoribonucleotides, is a purine rich region located between the two major transcriptional initiation sites P1 and P2. Possible involvement of p55 in a number of regulatory events is discussed.